Basic Engine(the Best)

Caterpillar EngineFundamentalsCourse Overview

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This course introduces the student to basic diesel engine theory andservice procedures. Caterpillar engine systems and applications willbe studied. Several Caterpillar Engines will be presented withemphasis on the 3406 due to its high field population.

The following course curriculum has been developed using thereference materials and tooling listed on the following pages.Substitute materials and tooling may be used at the discretion of theinstructor.

Course Exercises and lab assignments may require modification ifsubstitute materials and tooling are used.

Table Of ContentsUNIT 1: Introduction to Caterpillar Diesel Engines

Lesson 1: Caterpillar Engine Product Line, ApplicationsLesson 2: Diesel Engine Components and OperationLesson 3: Engine Performance Terminology

UNIT 2: Air Intake and Exhaust SystemsLesson 1: Intake and Exhaust System Components, Operation,

and MaintenanceLesson 2: Remove, Inspect, and Install Air and Exhaust System

Components

UNIT 3 Lubrication Systems and OilLesson 1: Lube System Components and OperationLesson 2: Remove, Inspect, and Install Lube System

Components

UNIT 4: Cooling SystemsLesson 1: Cooling System Components and OperationLesson 2: Remove, Inspect, and Install Cooling System

Components

UNIT 5: Diesel Fuel and Mechanically Controlled Fuel SystemsLesson 1: Diesel FuelLesson 2: Caterpillar 3406 New Scroll Fuel SystemLesson 3: Remove, Inspect, and Install Fuel System

ComponentsLesson 4: Caterpillar Sleeve Metering Fuel SystemsLesson 5: 3116/26 Mechanical Unit Injector Fuel Systems

UNIT 6: Engine Disassembly, Inspection, and AssemblyLesson 1: 3406 Disassembly and InspectionLesson 2: Caterpillar 3406 Engine maintenance

UNIT 7: Electronically Controlled Fuel SystemsLesson 1: Caterpillar Electronic Fuel Systems

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Caterpillar EngineFundamentalsObjectives O

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This course prepares Caterpillar dealer entry-level service techniciansfor more advanced training on specific engines and systems. Aftersuccessfully completing this course, a student will be able to:

- Identify the wide range of engines in the Caterpillar Product Line.- Identify various diesel engine applications.- Explain basic diesel engine theory.- Define engine performance terms.- Identify basic diesel engine components and their function.- Describe the following engine systems:

Air intake and exhaust systemsLubrication systemCooling systemFuel system and governor

- Demonstrate the ability to disassemble and inspect Caterpillar3406 diesel engine with a mechanical governor.

- Demonstrate the ability to reassemble and perform necessaryadjustments on a Caterpillar 3406 diesel engine with a mechanicalgovernor.

- Explain the operation of the Caterpillar Sleeve Metering FuelSystem.

- Explain the operation of the Caterpillar 3116/26 Mechanical UnitInjector Fuel System.

- Explain the operation of and identify components used inCaterpillar electronically controlled engines using EUI and HEUIfuel systems.

Lesson 1: Caterpillar Engine Product Line and Applications

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Objective:

At the completion of this lesson the student will be able to identify awide range of Caterpillar engines and their applications.

References:

Industrial Engine Selection Guide LECH9163Harness the Power (Cat Truck Engines for 1998) LEXT8138Caterpillar Marine Engine Selection Guide LECM8477

Introduction:

Caterpillar engines are known around the world for their durability,performance, and efficiency. Whether they are used in earthmovingequipment, on-road or off-road vehicles, industrial power situations,marine installations, or electric power generation, Caterpillar engineshave set new standards for decades. To give customers a competitiveadvantage, Caterpillar is constantly working to push performance tohigher levels.

Today's line of Caterpillar engines offers some of the most advancedengineering features available. These include electronic controls,hydraulically actuated electronically controlled unit injectors (HEUI),and other exclusive technologies that dramatically reduce engineemissions.

Lesson 2: Identify Caterpillar Diesel Engine Components and Explain Principles of Diesel Engine Operation

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Objective:

The student will be able to identify diesel engine components andexplain the principles of diesel engine operation.

References:

The Engine Book LEBQ9801Introduction to Diesel Engines TECB60053400 Engine Major Component Performance Guide SEBD07943406 Engine Components and Systems CD-ROM

Introduction:

Caterpillar develops and builds four-stroke-cycle diesel engines tosatisfy the requirements of Caterpillar-built equipment as well as awide variety of equipment built by other manufacturers.

To effectively perform diagnosis, repair, and service, it is necessaryto have a complete understanding of the operating principles andconstruction of diesel engines.

This CD-ROM presentation will review the major engine componentsand systems of the Caterpillar 3406B diesel engine.

Fig. 1.2.1 Caterpillar 3406B Engine

Caterpillar 3406B Engine

Years of diesel experience have provided Caterpillar with thetechnology necessary to design and build high quality engines thatoffer maximum performance at a low overall cost. The specificdesign considerations for the 3406B include:

Reliability

Serviceability

Long Life before Overhaul is Needed

Low Overhaul costs

Application Flexibility

Fuel Economy

Oil Control

Performance

Caterpillar has always emphasized strength and quality, and continuesto do so with the 3406B. The 3406B is a heavy-duty, in line, 6-cylinder, diesel engine. The engine has a 5.4 inch bore, 6.5 inchstroke and a displacement of 893 cu. in.

The major engine components will now be discussed in detail.

Fig. 1.2.2 Cylinder Block

Cylinder Block

One of the major components in a diesel engine that must exhibitmaximum strength is the cylinder block. To provide maximumstrength, the block is precision cast using a combination of alloys.

Fig. 1.2.3 Cylinder Head

Cylinder Head

The cylinder head is designed to have excellent structural strengthand ridgidity. The cylinder head has passed rigorous, deep thermalcycle shock testing for assured durability. This results in a cylinderhead with significant resistance to cracking.

The steel or aluminum spacer plate that is used between the cylinderhead and the block eliminates the need for deep counterbores in thecylinder block. Deep counterbores decrease the structural integrity ofthe block and are prone to cracking.

Fig. 1.2.4 3406B Crankshaft

Fig. 1.2.5 3406C Crankshaft

3406C Crankshaft

With the introduction of the 3406C, the size of the rod bearing hasbeen significantly increased (projected area by 19%). The widerbearing spreads the load over a greater surface area, dramaticallydecreasing the bearing load while increasing the bearing life. Thisphoto shows a former rod bearing on the new crankshaft todemonstrate the increase in bearing area. Additionally, this changeincreases the oil film thickness by 50% and gives the 3406C thelargest rod bearing capacity in its class, eliminating mid-life bearingroll-ins.

3406B Crankshaft

The crankshaft is a carbon steel forging that is total hardened. Manyother diesel engine manufacturers induction harden their crankshaftsonly at the journals and fillets. This process can leave a stress riser atthe boundary between the hardened and unhardened areas. Thepatented Caterpillar total-hardening process hardens the entire surfaceof the crankshaft, creating a longer wearing and stronger crankshaft.With the entire surface of the crankshaft hardened, the possibility ofcracking is reduced.

Fig. 1.2.6 Connecting Rods

Connecting Rods

The forged boron steel connecting rod is hardened and shot peenedfor stress relief. The tapered-end design provides additional pin tobore contact area during the power stroke. This results in extrastrength and durability of the piston and rod assembly.

New with the 3406C is a larger, stronger connecting rod with a muchlarger rod bearing. In fact, the wider 3406C rod bearing has thegreatest load carrying capacity of any heavy duty engine in its class.By spreading the firing loads over a larger surface area, load carryingcapacity, bearing reliability, and service life are all dramaticallyincreased for all ratings.

Fig. 1.2.7 Pistons

Pistons

Pistons are critical to the design, life, and overall performance of anengine. The Caterpillar 3406B Engine's three-ring piston is analuminum alloy casting with a cast-in nickel iron band for thecompression rings. The nickel iron band provides improved groovestrength and resists wear.

The three-ring piston design provides excellent compression and oilcontrol while reducing friction and heat buildup. This results inextended piston, ring and liner life and reduces maintenance cost atoverhaul time.

The piston rings are nodular iron for strength and durability. The oiland intermediate rings are chrome coated, while the top ring isplasma coated. Both coatings provide excellent wear and scuff-resistant properties.

Fig. 1.2.8 Cylinder Liners

Fig. 1.2.9 Valves

Valves

Exhaust and intake valves in the 3406B Engine are extremely wearresistant for long life. Three materials are used in the exhaust valves.The stems are made of a hardened stainless steel. A special alloy isused for the heads to provide high temperature strength. The seatingfaces of the valve are made of Stellite for high temperature wearresistance. Intake valve heads and stems are made from stainlesssteel and are hardened for resistance to wear.

Cylinder Liners

Cylinder liners are made of a cast molybdenum alloy iron for an extramargin of hardness. The internal surface of each liner is inductionhardened, then ground in a cross-hatched pattern to aid in oil control.O-rings are used to seal the liner to block coolant cavity. A liner bandis used to seal the top of the liner. Because the engine is rigid, theseseals remain seated and provide excellent liner sealing.

Fig. 1.2.10 Valve Seat Inserts

Fig. 1.2.11 Camshaft

Camshaft

The camshaft is made of a special alloy steel that is drop forged andhardened for reliability and durability. The camshaft gear is heatedand pressed on during installation.

Valve Seat Inserts

When the valve seats become worn or damaged, valve seat inserts arereplaceable. Intake inserts are a stainless steel alloy and the exhaustinserts are a nickel base alloy.

Each valve has a rotator which moves the valve face 3 relative to thevalve seat during one complete cycle of the engine. This assuresuniform wear for longer valve life and helps prevent burned valves.

Fig. 1.2.12 BrakeSaver

Fig. 1.2.13 Fuel System

Fuel System

The 3406B utilizes a direct injection, scroll type, high pressure fuelsystem. The system is very efficient, allowing short injectionduration and excellent fuel atomization. This results in loweremissions and improved fuel economy.

BrakeSaver

The 3406B has an optional BrakeSaver hydraulic retarder thatprovides smooth, quiet and efficient vehicle braking. The BrakeSaverdevelops a retarding capability of 360 hp and maintains normalengine temperatures on long downhill grades. The hydraulicoperation of the BrakeSaver provides smooth, gradual engagement,reducing the possibility of skids or jackknives.

By relieving the service brakes of the severe wear caused by downhillbraking, the BrakeSaver extends brake lining, drum, and tire life.This reduces user maintenance costs.

Fig. 1.2.14 Fuel Injection Nozzle

Fig. 1.2.15 Fuel Injection Pump

Fuel Injection Pump

Individual scroll-type fuel pumps for each cylinder require nobalancing and maintain fuel efficiency without periodic adjustment.

Fuel Injection Nozzle

Injection nozzles can be replaced in the field. The six hole tipatomizes the high pressure fuel flow in the combustion chamber forcomplete, efficient combustion.

Fig. 1.2.16 Spring/Hydraulic Timing Advance

Fig. 1.2.17 Hydraulic Timing Advance

Hydraulic Timing Advance

A double hydraulic automatic timing advance was introduced on the3406B Engines, serial number 4MG3600 and up. In this system, thetiming mechanism advances and retards hydraulically using engineoil. A spool valve actuated by flyweights controls the flow of oil inthe timing mechanism. This fully hydraulic system has a timingadvance capability of 12 degrees.

Spring Hydraulic Timing Advance

The speed sensitive timing advance mechanism optimizesperformance and makes starting easy. Earlier 3406B Engines used aspring/hydraulic system. As engine speed increases, timing isadvanced hydraulically using engine oil. As engine speed decreases,a large spring pushes the timing mechanism toward the retardedposition. The spring/hydraulic system has a timing advancecapability of 9 degrees.

Fig. 1.2.18 Governor

Fig. 1.2.19 Turbocharger

Turbocharger

3406B turbochargers are performance matched for each horsepowerrating. Their low inertia design reacts rapidly to load demands whiledelivering full-rated power to the altitude limit appropriate for theapplication of the engine. This results in improved combustionefficiency and more work per gallon of fuel.

Governor

The Caterpillar 3406B features a full range governor. Thehydraulically assisted governor maintains nearly constant speed overrolling terrain similar in effect to automatic speed control inautomobiles. This reduces gear shifts and accelerator changes,resulting in improved trip times and less driver fatigue.

Fig. 1.2.20 Engine Component Locations


Engine Component Locations

On the right side of the engine are the: Turbocharger

Exhaust manifold

Oil filter

Oil cooler

Breather and tube assembly


Located on the front of the engine are: Air compressor drive cover

Timing advance cover

Vibration damper

Coolant pump

Component Locations


Fig. 1.2.23 Transmission Oil Cooler


Located on the left side are the: Air compressor mounting location

Injection lines

Hand priming pump

Starter location

Fuel filter

Fuel transfer pump

Fuel injection pump

Depending on the application, the engine may also be equipped witha different arrangement on the fuel filter and priming pump locations.Some engines will also have an aftercooler.

Transmission Oil Cooler

If used, the transmission oil cooler is installed on the right side of theengine.

Lesson 3: Engine Performance Terminology

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Objective:

The student will be able to define essential engine performanceterminology and calculate engine displacement, compression ratio,and horsepower.

References:

Glossary of Terms LEXQ8150

Introduction:

To understand diesel engine design and performance, it is necessaryto know the terminology and math calculations that apply to dieselengines.

Fig. 1.3.1

There are many factors that determine the performance of an engine.The operating conditions that an engine is exposed to and the specificapplication an engine is placed in can affect the performance of theengine. Many of the determining factors for performance, however,are determined by the manufacturer of the engine.

Some of the basic specifications that a manufacturer makes on anengine that affect performance of the engine are:

Bore

Stroke

Displacement

Compression Ratio

The performance of an engine is typically rated by comparing poweroutput and/or efficiency of the engine. These evaluations can bemeasured in several different ways. The basis for thesemeasurements and the manufacturers specifications must be knownin order to better understand the effects that all of these factors andmeasurements have on engine performance.

BDC

TDC

STROKE

BORE

CRANKSHAFTAT TDC

CRANKSHAFTAT BDC

Fig. 1.3.2

Top Dead Center (tdc)

Top dead center (tdc) is a term used to describe the position of thepiston when the piston is at its highest point in the cylinder. Thisoccurs when the crankshaft and the connecting rod are fully extendedand straight with one another. Many events in the operation of theengine are identified by crankshaft position, measured in degreeseither before or after tdc.

Bottom Dead Center (bdc)

Bottom dead center (bdc) is a term used to describe the position ofthe piston when the piston is at its lowest point in the cylinder. Thisoccurs when the crankshaft and the connecting rod are fully retractedand straight with one another.

Bore (B)

Bore is a term used to describe the diameter of a single cylinder in anengine. Bore is typically measured in millimeters or inches.

Stroke (L)

Stroke is a term used to describe the distance that a piston travels inthe cylinder of the engine. The stroke is measured as the differencebetween the position of the piston at BDC to TDC. The amount ofstroke is determined by the design of the crankshaft. The stroke isequal to exactly twice the throw of the crankshaft. Stroke is typicallymeasured in millimeters or inches.

17 TO 1

DIESEL ENGINE

Fig. 1.3.3

Engine Displacement

The bore, the stroke, and the number of cylinders all determine thedisplacement of an engine. The displacement of an engine is simplythe amount of volume displaced by all cylinders in an engine duringone complete rotation. The displacement of an engine can becalculated using the following formula:

Displacement = x r2 x L x nWhere...

= 22/7

r2 = radius x radius

radius = 1/2 bore

L = stroke

n = number of cylinders in the engine

Compression Ratio

The compression ratio of an engine is determined by the cylinderdisplacement and the combustion chamber volume. In order tocalculate the compression ratio use the following formula:

CR = Total Cylinder Volume / Combustion Chamber Volume

Typical compression ratios of diesel engines range from 11:1 to22:1. This is significantly higher than the compression ratio of atypical gasoline engine. Diesel engines utilize higher compressionratios to increase the pressure within the combustion chamber.Higher pressures will cause an increase in the temperature of the airand fuel in the combustion chamber. This high temperature(approximately 1000F) will cause the diesel fuel to ignite withoutthe use of a spark plug.

12,000 FT.9.3 PSI

8,000 FT.10.9 PSI

4,000 FT.12.7 PSI

3657 M.64.12 kPa

2438 M.75.15 kPa

1219 M.87.50 kPa

101.35 kPa SEA LEVEL SEA LEVEL 14.7 PSI

EARTH'S SURFACE

WEIGHT OFAIR ON

EARTH'SSURFACE

Fig. 1.3.4

As an example, due to increased pressure at sea level the air is moredense than the air on top of a mountain. The dense air allows formore air molecules to flow into the cylinder. This allows for the fuelto be more completely burned in a diesel engine, which producesmore power. This is why engines perform better in lower altitudes,the air is more dense.

Ambient air temperature also plays a role in how much air can flowinto an engine. The lower the temperature of the air, the more densethe charge of air is that enters the cylinders. The greater the densityof the air, the more power that can be produced efficiently in theengine.

Humidity is also an important factor in diesel engine combustion.Humidity is a relative measure of the amount of moisture that issuspended in the air. The suspended moisture has a cooling effect onthe air as it enters the engine. Therefore, the greater the humidity ofthe air, the colder the air, the denser the air, the more power that canbe produced efficiently in the engine.

Atmospheric Conditions

In order to produce the desired levels of power, diesel engines requirea large volume of air. Therefore the atmospheric pressure, theambient air temperature, and the relative humidity of the air play alarge role in the performance characteristics of the engine.

It is the atmospheric air pressure that is present that forces the air intothe engine. Atmospheric pressure is the pressure that is exerted onthe earths surface due to the weight of the atmosphere (the airsurrounding the earth). Atmospheric pressure is greatest at sea levelbecause there is more air above the air at sea level than there is abovethe air at the top of a mountain. Refer to figure...

Unit 2Air Intake and Exhaust Systems

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Unit Objectives:

The student will be able to:

1. Identify air intake and exhaust system components in anengine installation.

2. Remove, inspect, and install air and exhaust systemcomponents on a Caterpillar 3406B or 3406C engine.

Lesson 1: Identify Air Intake and Exhaust Systems

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Objectives:

The student will be able to explain the operation of the air intake andexhaust system and identify related components.

References:

Air Intake and Exhaust Presentation CD-ROM3406E Operation and Maintenance Manual SEBU6758Turbochargers SEBV0550Air System Specifications Handout Copy

Introduction:

Efficient diesel engine operation requires that the proper amount ofair can enter the combustion chamber and the exhaust gases can exitwith minimal restriction. Both inlet air and exhaust gas temperaturesare also critical for maximum engine performance and life.

Air Inletand

Exhaust System

Fig. 2.1.2 Air System Components.

Fig. 2.1.1 Introduction

Air System Components

The Air Inlet and Exhaust System contains the following components:

Air cleaner

Turbocharger

Aftercooler

Cylinder head, valves, and pistons

Exhaust manifold

Introduction

This first system we will discuss is the Air Inlet and Exhaust system.

Fig. 2.1.3 Air Cleaner

Air Cleaner

Air is drawn into the engine through the air cleaner. The air cleanerhouses a filter element which removes foreign material from the airbefore it enters the engine. There are several different types of aircleaners currently available on Caterpillar engines. Always refer tothe operation and maintenance manual of the engine for the mostaccurate maintenance procedures.

Fig. 2.1.4 Typical Service Indicator

Engine air cleaners should be serviced on a regular basis. Many aircleaners are equipped with a service indicator. The indicatormonitors the amount of restriction through the air cleaners. Theservice indicator is the most accurate method to use to determinewhen the air cleaners are in need of service. Engine air cleanerelements should be serviced, cleaned or replaced, when either theyellow diaphragm enters the red zone or the red piston locks into thevisible position.

Fig. 2.1.5 Dry Element Air Cleaner

Fig. 2.1.6 Dry Element Cleaning

Dry element air cleaners can usually be cleaned with filtered, dry airwith a maximum pressure of 207 kPa (30 psi). The element shouldbe cleaned from the clean side out, holding the tip of the air nozzleparallel to the pleats of the air cleaner.

Dry element air cleaners are by far the most common type of aircleaners used on Caterpillar engines. Dry element air cleaners aretypically composed of a pleated paper filter media that is used toremove the dirt from the incoming air.

This type of air filter requires replacement or cleaning when theservice indicator is tripped.

Fig. 2.1.7 AIRSEP Filters

Another type of air cleaner that is found on Caterpillar engines, mostcommonly in high performance marine applications, is the AIRSEP.The AIRSEP elements are a pleated fiber filter media that isimpregnated with a special petroleum based fluid. This allows theAIRSEP elements to flow a high volume of air with little restriction,but still clean the air before it enters the engine. These elements arereusable, but the elements require a special maintenance procedure.The AIRSEP filters must be cleaned using the 102-9720 Cleaning Kit.Follow the guidelines in the operation and maintenance manual.

Fig. 2.1.8 Simple Cap Precleaner

Fig. 2.1.9 Dust collection bowl

Another type of precleaner that is used on Caterpillar equipment is aspirally vaned drum. The vanes cause the incoming air to spin.Because the dirt that is drawn in is heavier than the air, the dirt isforced to the outside due to the spinning action. The dirt then fallsinto a collection bowl.

Precleaners should be inspected and emptied on a daily basis.

Precleaner

Many engines are also equipped with a precleaner. The precleaner islocated before the inlet to the main air cleaner. The purpose of theprecleaner is to collect much of the dirt before the air cleaner. Thisincreases the service life of the air cleaner.

The simplest type of precleaner is a simple mesh cap at the top of theair filter housing inlet.

Fig. 2.1.10 Turbocharger

Turbocharger

Many diesel engines are equipped with a turbocharger in order toimprove the performance and the efficiency of the engine. Theturbocharger receives clean air flow from the air cleaner. Therotation of the turbocharger compressor wheel draws air in,compresses it and delivers it under pressure to the cylinders.

Advantages of Turbochargers Power Efficiency

Fig. 2.1.11 Advantages of Turbochargers

Advantages of Turbochargers

Turbocharging has several important advantages:

1. Power - Compressed air has more oxygen per volume. With moreoxygen in the cylinder, more fuel can be injected for a higherenergy output.

2. Efficiency - Turbocharging allows a more efficient combustion forimproved emissions and fuel consumption.

Fig. 2.1.12 Turbocharger Operation

Turbocharger Operation

When the turbocharger compresses the intake air, the temperature ofthe air is increased. Hot air has less density, thus less oxygen. If thehot compressed air is delivered to the engine, some of the efficiencygained by compression will be lost. This is where the aftercoolercomes into play. The aftercooler lowers the temperature of the airbefore its enters the cylinders.

Aftercooler Air to Air Aftercooler Jacket Water Aftercooler

Fig. 2.1.13 Aftercooler

Aftercoolers

Aftercoolers are used in conjunction with turbochargers in order tolower the temperature of the air coming from the turbocharger beforethe air enters the cylinders. This causes the air to be more dense,therefore contain more oxygen in a given volume. This increase inoxygen in the cylinders translates into greater power and efficiencyfrom the engine.

There are different types of aftercoolers that are used on Caterpillarengines: All aftercoolers serve the same purpose however, removeheat from inlet air providing cooler and more dense air to thecylinder.

Fig. 2.1.15 Jacket Water Aftercooler (JWAC)

Jacket Water Aftercooler (JWAC)

The jacket water aftercooler system has a coolant charged coreassembly. It uses the engine coolant in order to cool the air chargeentering the cylinders. Coolant from the water pump flows throughthe aftercooler core. Pressurized air from the turbocharger is cooledby the aftercooler before entering the intake manifold.

Air to Air Aftercooler (ATAAC)

With the air to air aftercooled system, a separate cooler core isinstalled in front of the vehicle engine radiator. Ambient temperatureair is moved across the aftercooler core by the engine fan.Pressurized air from the turbocharger is cooled by the air to airaftercooler before entering the intake manifold. This is an extremelyeffective method for cooling the turbocharged air when a largevolume of fresh cool air can be pushed through the aftercooler. Forthis reason this is the configuration found most often in on-highwaytruck applications.

Fig. 2.1.14 Air to Air Aftercooler (ATAAC)

AFTERCOOLER

AUXILIARYWATER PUMP

AFTERCOOLER WATERCOOLING CIRCUIT

JACKET WATERCOOLING CIRCUIT

TURBOCHARGER

JACKETWATERPUMP

SEPERATE CIRCUIT AFTERCOOLER

Fig. 2.1.16 Separate Circuit Aftercooler

Separate Circuit Aftercooler (SCAC)

A separate circuit aftercooler system is similar to the jacket wateraftercooler system with minor differences. A separate cooling circuitfrom the jacket water of the engine is used to cool the engine. Thejacket water acts as normal, cooling the engine head, block,transmission oil, etc. The separate circuit aftercooler system has adedicated water pump, lines, and heat exchanger for the aftercooler.This system is typically used in applications where maximumaftercooling is required. Many marine applications utilize separatecircuit aftercoolers in conjunction with a heat exchanger that isdesigned to use the keel water for cooling the circuit. Many ofCaterpillars large mining trucks also use this type of aftercooler.

Fig. 2.1.17 Intake Stroke

Intake Stroke

Air fills the inlet ports in the cylinder head. On the INTAKE strokeas the piston travels down in the cylinder the intake valves open, andair fills the volume of the cylinder.

From the air cleaner (turbocharger/aftercooler, if equipped) theincoming air enters the inlet manifold. The inlet manifold directs theair into the cylinder head.

Fig. 2.1.18 Compression Stroke

Fig. 2.1.19 Power Stroke

Power Stroke

When the piston nears the top of its travel, fuel is injected into thecylinder. The fuel mixes with the hot air and combustion begins.The energy released by the combustion forces the piston downproducing the POWER stroke.

Compression Stroke

On the COMPRESSION stroke, as the piston begins to travel up, theintake valves close. The air that is trapped in the cylinder iscompressed. Compressing the air raises the air temperature to a pointwhere it will cause fuel to ignite when it is injected into the cylinder.

Fig. 2.1.20 Exhaust Stroke

Fig. 2.1.21 Exhaust Flow

Exhaust Flow

Exhaust gases leaving the cylinder enter the exhaust manifold and arethen routed to the turbocharger, if equipped.

The hot exhaust gases flowing out of the cylinders contain substantialunused heat energy. The turbocharger exhaust turbine captures someof this heat energy.

Exhaust Stroke

Near the end of the POWER stroke the exhaust valves open. Anyresidual pressure from combustion will rush into the exhaustmanifold. On the upward or EXHAUST stroke the gases are pushedout of the cylinder by the piston. At the top of the stroke the exhaustvalves close and the cycle starts over.

Fig. 2.1.22 Turbocharger Operation

Fig. 2.1.23 Exhaust Flow

Exhaust Flow

From the turbocharger (if equipped), the exhaust gases pass throughthe exhaust pipe, the muffler, and the exhaust stack.

Turbocharger Operation

The exhaust gases flow past the blades of the turbine wheel and causethe turbine wheel to rotate. The turbine wheel is connected by a shaftto the compressor wheel. The exhaust gases push the turbine andsubsequently the compressor wheel to a high RPM, about 80,000 -130,000 RPM. This causes the intake air to be compressed.

When the load on the engine increases, more fuel is injected into thecylinders. The increased combustion generates more exhaust gasescausing the turbine and compressor wheel to turn faster. As thecompressor wheel turns faster, more air is forced into the engine.Themaximum rpm of the turbocharger is controlled by the fuel setting,the high idle speed setting and the height above sea level.

CATERPILLAR ENGINE AIR SYSTEMS SPECIFICATIONS

Maximum inlet air temperature - 120F ambient

Maximum air cleaner restriction -New filter - 15" H2O

Used filter - use air filter service indicatorOn-highway diesel engines - 25" H2O

Other diesel engines - 30" H2O

Natural gas engines - 15" H2O

Maximum aftercooler restriction -Jacket Water Aftercooler - 3" HgAir-to-Air Aftercooler - 4" Hg

Maximum exhaust temperature -Turbocharged - 1200F (a small number of engines may be higher)Naturally aspirated - 1300F

Maximum exhaust restriction -Turbocharged - 27" H2O

Naturally aspirated - 34" H2O

On-highway diesel engines - 40" H2O

Maximum inlet manifold temperatures -Turbocharged - 325FTurbocharged, Jacket Water Aftercooled - 245FTurbocharged, Separate Circuit Aftercooled (85F water) - 125FTurbocharged, Air-to-Air Aftercooled - 150F

Conversion data -.5 psi = 1" Hg = 1' H2O = 3.5 kpa

1 psi = 2" Hg = 2' H2O = 7 kpa

15 psi = 30" Hg = 30' H2O = 103 kpa

Unit 3Lubrication Systems and Oil

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Unit Objectives:


1. Explain the function of the engine lubrication system and itscomponents.

2. Identify proper oil classifications for diesel engines.3. Explain a normal oil maintenance schedule for a Caterpillar

3406E engine.4. Remove, inspect, and install lubrication system components

on a Caterpillar 3406B or 3406C engine.

Unit References:

3406 Lube System Presentation CD-ROMOil Development at Caterpillar CopyCG-4, The Preferred Oil LEDQ7315Oil and Your Engine SEBD0640Oil in Your Engine LEVP90013406E Operation and Maintenance Manual SEBU67583406B Service Manual SEBR05443406C Service Manual SEBR0550Unit 3 Quiz Copy

Tooling:

8T0461 Servicemans Tool Set or Equivalent1U5750 Diesel Engine Repair Stand1U5749 Engine Adapter Plate

Lesson 1: Identify Lubrication System Components and Their Operation.

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Objectives:

The student will be able to explain the operation of the lubricationsystem and identify related components.

References:

3406 Lube System Presentation CD-ROMOil Development at Caterpillar CopyCG-4, The Preferred Oil LEDQ7315Oil and Your Engine SEBD0640Oil in Your Engine LEVN90013406E Operation and Maintenance Manual SEBU6758

Introduction:

The lubrication system in a diesel engine is more important than everdue to the demands of the high performance, low-emission enginesof today. Not only is the lube system required to provide clean oil tothe proper places in the engine but the oil itself must withstandhigher temperatures and extended drain intervals while maintaining alow rate of consumption.

Fig. 3.1.2 Lubrication System Components

Lubrication System Components

The lubrication system contains the following components:

1. Oil pick-up tube and suction bell2. Oil pump3. Oil pressure relief valve4. Oil cooler bypass valve5. Oil cooler6. Oil filter bypass valve7. Oil filter8. Oil supply to turbocharger9. Oil supply to engine

Introduction

This presentation covers the lubrication system of a Caterpillar 3406Bor 3406C engine for illustrative purposes. Refer to the systemsoperation manual for a particular engine of interest.

Fig. 3.1.1 Caterpillar 3406 Engine

This presentation will review components and operation of aCaterpillar 3406 lube system. This system is typical of a Caterpillarengine, but some engines will differ. Engines that use the HEUI fuelsystem will differ significantly.

Fig. 3.1.3 Oil Passages

Fig. 3.1.4 Front Gear Train Lubrication

Front Gear Train Lubrication

The lubrication for the front gear train includes the:

1. Oil supply to idler gear shaft2. Oil supply to accessory drive

Lets trace the flow of oil through each component.

Oil Passages

The lubrication system inside the engine includes the followingcomponents:1. Oil manifold (gallery) in block2. Piston cooling jet3. Oil passage to main and cam bearings4. Camshaft and main bearing oil passage5. Front oil supply for lifters6. Rear oil supply for lifters7. Front oil supply to rocker shaft8. Rear oil supply to rocker shaft9. Oil supply to fuel pump

Fig. 3.1.5 Oil Pump Oil Flow

Fig. 3.1.6 Oil Pump Description

Oil Pump Description

The oil pump is a positive displacement gear type pump, driven bythe crankshaft gear.

Oil Pump Oil Flow

Lubricating system flow begins as the pump draws oil from the oilpan sump. The oil pump pick up tube has a suction bell at the openend which is located low in the pan sump. The suction bell containsa screen to prevent foreign material from entering the oil pump.

Many Caterpillar engines are designed to work in applications thatmay require the engine be at a steep angle. A track type tractor forexample, typically is used in applications that require the machineand engine be at a relatively steep angle from the horizontal. In orderto ensure that all of the engine oil does not collect in one end of theoil pan, away from the suction bell, many engines also have ascavenge oil pump. A scavenge oil pump is nothing more than an oilpump that ensures that there is always oil in the main sump. Thiskeeps the lubrication system from being starved of oil at steep slopes.

INLET OILOUTLET OIL

HOUSING

DRIVE GEAR

IDLER GEAR

FORCE

MESHING GEAR TEETH

Fig. 3.1.7 Gear Pump

OUTERGEAR

INNERGEAR

OUTLETPORT INLETPORT

Fig. 3.1.8 Rotor Pump

Some Perkins engines use a rotor type pump. This pump has an innergear and a outer gear that are in mesh with one another. The innergear is driven by the engine. The centerline of the outer gear is offsetfrom the inner gear and is free to turn. As the inner gear is turned itcauses the outer gear to rotate. Engine oil is drawn into the pumpthrough the inlet and carried in the space between the two rotatingparts to the outlet. On the outlet side the inner gear and the outergear come into mesh with one another and force the oil to be pushedout the outlet port of the pump.

The basic gear pump is the type most commonly found on Caterpillarengines. This pump has two gears in mesh. One gear is driven bythe engine and the other is an idler gear. The two gears rotate inopposite directions capturing the engine oil, and drawing it aroundthe inside of the housing. When the teeth come together in mesh theoil is forced out of the teeth and flows through the pump outlet to therest of the lubrication system.

Fig. 3.1.9 Oil Pump Relief Valve

Fig. 3.1.10 Oil Pump Relief Valve

Oil Pump Relief Valve

The valve will remain on its seat (closed) until the oil pressure at thepump rises above the pressure that is exerted by the spring in thevalve.

As pressure in the system nears the maximum, it will force the valveoff its seat and allow some oil to bypass to the low pressure side ofthe pump. If the pressure in the system continues to rise, the valveplunger will move farther down allowing more flow to bypass.

When the engine oil is cold it will be thick or have a high viscosity,and will resist flowing. During cold engine start ups the oil willresist flowing through the engine. Pressure will build quickly,causing the valve to open.

Oil Pump Relief Valve

The oil pump has an integral pressure relief valve which controls themaximum system operating pressure. Limiting the pressure helps toreduce leaks and prolong seal life.

Fig. 3.1.11 Oil Cooler

Fig. 3.1.12 Oil Cooler Bypass Valve

Oil Cooler Bypass Valve

During cold start ups, the cold oil will also resist flowing through theoil cooler. To prevent this resistance from causing oil starvation, anoil cooler bypass valve is incorporated into the cooler assembly. Thisbypass valve senses oil pressure between the inlet and outlet of thecooler. It is designed to open and bypass oil flow around the coolerwhen the oil is cold and thick.

Oil Cooler

Many engines are equipped with an oil cooler assembly. The coolerutilizes an engine oil to coolant heat exchanger. Hot engine oilpassing through the cooler element transfers heat to the enginecoolant. This cooling of the oil helps to maintain the lubricatingproperties of the oil under heavy engine load.

Fig. 3.1.13 Oil Filter

Fig. 3.1.14 Oil Filter Bypass Valve

Oil Filter Bypass Valve

The engine oil flows in the outside of the filter, through the filtermedia, and out the hole in the center of the filter under normaloperating conditions. However, the filter element resists cold oilflow. It also resists oil flow when it becomes dirty. To preventdamage to the element and possible oil starvation to the system, thefilter base is equipped with a filter bypass valve. The bypass valvesenses the pressure differential across the element and will open,bypassing oil flow around the element if the pressure becomesexcessive. This is one reason why proper maintenance procedures areso important. Dirty filters can lead to serious problems.

Oil Filter

The oil filter base mounts at least one filter element. Most Caterpillarengines use spin-on style full flow filters in order to removedamaging foreign materials from the engine oil.

Fig. 3.1.15 Turbocharger Lubrication

Fig. 3.1.16 Piston Cooling Jets

Piston Cooling Jets

Clean, cooled oil is directed from the filter base to the oil manifold inthe engine block. The piston cooling jets are connected to the oilmanifold and direct a small stream of oil to the underneath side of thepistons for cooling. This helps to cool the pistons to a uniformtemperature and provide a longer service life of the pistons.

Turbocharger Lubrication

The turbocharger oil supply line is connected to the outlet of the filterbase. An adequate supply of cooled, clean oil is essential toturbocharger life. Thus, the turbocharger receives oil flow beforeother engine components. Oil cools, and lubricates the bearings ofthe turbocharger. Oil flow from the turbocharger is returned to the oilpan. This is also why hot shutdowns or high rpm shutdowns of theengine are bad. Insufficient oil flow under these conditions couldlead to premature failure of the turbocharger. The turbocharger needsthe oil to cool and to lubricate its bearings.

Fig. 3.1.17 Oil Supply to Bearings

Fig. 3.1.18 Oil Supply to Crankshaft Bearings

Oil Supply to Crankshaft Bearings

A groove around the inside of the upper main bearing shells suppliesoil flow to internal drilled passages in the crankshaft. The internalcrankshaft passages supply oil to the connecting rod bearings.

Oil Supply to Bearings

Each pair of main and camshaft bearings is connected by an oilpassage that is drilled in the block. The drilled passage receives oilthrough an intersecting drilled passage that is connected to the oilmanifold.

Fig. 3.1.19 Valve Lifter Lubrication

Fig. 3.1.20 Rocker Shaft Lubrication

Rocker Shaft Lubrication

The rear rocker shaft receives oil flow from the rear valve lifter oilpassage. The front rocker shaft receives oil flow from a drilledpassage connected to the front camshaft supply passage.

Drilled passages in the rocker shafts supply the upper valve train withoil flow. This is also used to supply oil to the compression releasebrake (Jake Brake), if equipped.

Valve Lifter Lubrication

A groove around the outside of the front and rear camshaft bearingssupply oil flow to the front and the rear valve lifter passages. Eachlifter body, roller and lower push rod socket receive lubrication fromthese passages.

Fig. 3.1.21 Front Gear Train Lubrication

Fig. 3.1.22 Air Compressor Lubrication

Air Compressor Lubrication

The air compressor receives oil from the oil passage to the accessorydrive, through passages in the timing gear housing and the accessorydrive gear.

Front Gear Train Lubrication

The front gear train idler gear and the accessory drive receive oil flowfrom an internal drilled passage that is connected to the frontcamshaft oil passage.

Fig. 3.1.23 Fuel System Lubrication

Fig. 3.1.24 Caterpillar BrakeSaver

BrakeSaver Option

Since the BrakeSaver retarder option becomes an integral part of thelubrication system, we will review the operation of the BrakeSaveralong with the changes to the lubrication system the option requires.

As we learned earlier, the BrakeSaver retarder is a hydraulic retarderthat provides smooth, efficient vehicle breaking on long downhillgrades.

Fuel System Lubrication

In a typical Caterpillar pump and line fuel system the fuel pump,governor and hydraulic timing advance unit receive oil flow from aport on the side of the block. This port is connected to the numberthree main and camshaft passage.

Fig. 3.1.25 BrakeSaver Oil Pump

Fig. 3.1.26 Oil Pump Bypass Valve

Oil Pump Bypass Valve

When the oil is cold, the high viscosity causes the bypass valve toopen and drain the oil from the rear section of the pump back into theoil pan.

Brake Saver Oil Pump

Engines equipped with a BrakeSaver retarder have a two section oilpump. The front section of the pump supplies oil for the lubricationof the engine. The path of the oil from the front section is the sameas the standard oil pump, except the oil does not go to the oil cooler.The oil from the front section of the pump flows directly to the oilfilter.

The rear section of the oil pump supplies oil for BrakeSaver operationand oil cooling.

BrakeSaver Control

Fig. 3.1.27 BrakeSaver Control

BrakeSaver Control

When the BrakeSaver retarder is in operation, the braking forceavailable is in direct relation to the amount of oil in the compartment.The BrakeSaver control valve determines the amount of oil deliveredto the unit.

Fig. 3.1.28 BrakeSaver Operation


BrakeSaver Operation

If the BrakeSaver control lever is in the ON position, air pressuremoves the valve spool to the right against the spring force. Engineoil from the oil pump is sent through the control valve to theBrakeSaver. After the oil goes through the BrakeSaver, it returns tothe BrakeSaver control valve. The valve then directs the oil to the oilcooler. From the cooler, the oil again returns to the control valve andis sent back to the oil pan.


When the oil is warm, the oil is sent to the BrakeSaver control valve.If the BrakeSaver control lever is in the OFF position, spring forceholds the valve spool against the cover at the air inlet end of thecontrol valve. With the valve spool in this position, the valve directsthe warm oil to the oil cooler. From the oil cooler the oil goes backthrough the BrakeSaver control valve and returns to the oil pan.

Fig. 3.1.30 BrakeSaver Lubrication

Fig. 3.1.31 BrakeSaver Components

BrakeSaver Components

The BrakeSaver housing is fastened directly to the rear face of theflywheel housing. The BrakeSaver retarder consists of the housing,stator and rotor. The rotor is attached to the crankshaft and rotates ina space between the stator and the housing.

BrakeSaver Lubrication

Lubrication for the BrakeSaver retarder is provided by an outside oilline from the engine lubrication system. This oil lubricates the pistonring seals and the lip-type seals under all conditions of BrakeSaverretarder operation. The drain line returns the oil to the oil pan.

Fig. 3.1.32 BrakeSaver Rotor

Fig. 3.1.33 BrakeSaver Housing

BrakeSaver Housing

The BrakeSaver housing and the stator are fastened to the flywheelhousing and cannot turn. Both the housing and the stator havepockets on their inside surfaces in alignment with the pockets in therotor.

BrakeSaver Rotor

The rotor has pockets on the outer circumference of both sides andfour holes to permit equal oil flow to both sides.




If the area in the stator and housing were smooth, the rotor and oilwould turn inside the compartment with little opposition. However,both the stator and housing have vanes which are opposite the rotor.These vanes oppose the flow of the oil in the compartment inducedby the rotor. It is this resistance of the oil flow that creates theretarding action of the BrakeSaver retarder.

This resistance to the oil flow creates heat in the oil which is removedby the oil cooler.


When the BrakeSaver retarder is in operation, engine oil comes intothis compartment from a passage in the bottom of the housing. Therotor, turning with the crankshaft, throws this oil outward into thestator and the housing compartment. The pockets or vanes on theturning rotor, force the oil to flow in the BrakeSaver compartment.

ENGINE OIL FUNCTIONS

In the modern diesel engine, engine oil must perform four basic taskswithout having a negative impact on engine performance andlongevity of the engine. These functions of the oil are discussedhere.

Lubrication

The engine oil provides a film of protection between the movingparts of the engine. This oil film reduces friction, wear, and heat inthe engine. In order to maintain the proper thickness of this oil filmthe engine must run at the correct temperature, the engine oil pumpmust produce the correct pressure, and the oil must have the correctviscosity.

Cooling

The combustion that takes place in the engine produces a tremendousamount of heat, especially on the pistons. The engine oil is theprimary cooling agent for the pistons. Much of the heat is removedby the oil that is between the cylinder wall and the piston and by"splash" oil thrown off moving parts. Additionally, many engineshave piston cooling jets that spray oil at the underside of the pistons,providing a tremendous cooling effect to the pistons. This is aprimary reason that engine oil is required to withstand hightemperatures without losing its properties.

Cleaning

As the engine operates there will be some amount of blowby. Therewill also be some amount of foreign debris in the engine from onesource or another. It is the responsibility of the engine oil to carrythe contaminants out of the moving engine components, so that thecontaminants will be cleansed from the system by the engine oilfilter. This is especially important in the engines equipped with theHEUI fuel system. The HEUI fuel system uses engine oil to operate.The engine oil helps to keep contaminants from collecting in theengine.

Sealing

The engine oil creates a film between the piston rings and thecylinder walls. This film not only lubricates, but also helps to sealthe combustion chamber of the engine off from the crankcase. Thishelps to prevent blowby.

OIL DEVELOPMENT AT CATERPILLAR

Lubricating oil used in the first Caterpillar Diesel, introduced in 1931, was straight mineral crankcaseoil. When the engines began experiencing ring sticking and cylinder liner scratching, it becameapparent that a more effective oil was needed. In 1935, the first additive crankcase oil was developedin a cooperative effort of several U.S. oil companies and Caterpillar.

The performance standards for this and subsequent oil were established by tests performed on a singlecylinder test engine designed and built by Caterpillar specifically for oil testing. This initial crankcaseoil was named "Superior Lubricants for Caterpillar Engines" and was sold only through CaterpillarDealers.

The test, run by engine manufacturers, required that the single cylinder test engine be disassembledafter it had run for a designated period of time at a pre-determined load and speed. Pistons wereinspected, and the color change caused by lacquering was observed and recorded. Other critical factorssuch as ring wear and deposits were measured. In 1958, Caterpillar established the Series 3classification.

It wasnt until 1970, that the API (American Petroleum Institute) recognized the need to revise itsclassification system. The API, SAE, and ASTM collaborated in this effort. Their new system wasbased on the same type of performance specifications which Caterpillar and others had been using.

Caterpillar was able to drop its classification system in 1972. The new API/SAE system establishedCD, CC and other SAE letter designations for oil classifications. These referred to performance levelsin engine tests. A list of all brand name API-rated oils is included in the Engine ManufacturersAssociation Lubricating Oils-Data Book, available from your Caterpillar Dealer, Caterpillar formnumber SEBU5939.

Caterpillar recommends that you use (SOS) Fluid Sampling, a service offered by most CaterpillarDealers. An analysis of your engine oil can show the presence of metal wear particles which canindicate acid attack or other abnormal wear. Before taking an oil sample, operate the engine until it isat the normal operating temperature. A sampling valve and adapter is available to take an oil samplewhile the engine is running. Fill the new sample bottle approximately 75% full. If a sample is takenfrom the oil drain stream do not get the sample from the first part or the last part of the oil drain. Usecaution to prevent burns or injuries caused by the hot oil. Fill out the sample and shipment labels.Make sure engine serial number, miles on oil, and unit number are indicated.

Lab Exercises:

Using a lab engine, explain lubrication system and componentsincluding oil cooler, oil filter, sump, and location of oil pump.

Install the engine onto a 1U5750 repair stand with 1U5749 adapter.

Using the appropriate 3406 Service Manual as a guide, remove theoil filter base from the 3406 lab engine and disassemble. Take noteof the oil filter bypass valve.

Remove oil cooler taking note of core and circulation path of oil andpath of coolant.

Remove oil pan and oil pump. Disassemble oil pump taking note ofgears and relief valve. Inspect oil pump using specifications from theService Manual.

Install lubrication system components removed in previousprocedures using the Service Manual as a guide.

UNIT 4Cooling Systems

Uni

t 4:

Coo

ling

Syst

ems

Unit Objectives:


1. Identify the components of engine cooling systems and explaintheir function.

2. Explain cooling system maintenance and characteristics of dieselengine coolant.

3. Remove, inspect, and install cooling system components on aCaterpillar 3406B or 3406C engine.

Unit References:

Cooling System Design Fundamentals LEKQ7353Coolant and Your Engine SEBD0970A Close Look at Cat Extended Life Coolant LEDQ73303406B Service Manual SEBR05443406C Service Manual SEBR0550Unit 4 Quiz Copy

Tooling:

8T0461 Serviceman's Tool Set or equivalent9S8140 Pressurizing Group5P0957 Battery/Coolant Tester8T5296 Coolant Test Kit

Lesson 1: Identify Cooling System Components and Function

Les

son

1: C

oolin

g Sy

stem

Com

pone

nts

Objectives:

The student will be able to explain the operation of the enginecooling system and identify related components.

References:

Cooling System Design Fundamentals LEKQ7353Coolant and Your Engine SEBD0970A Close Look at Cat Extended Life Coolant LEDQ7330

Introduction:

A diesel engine is dependent on the cooling system to achievemaximum performance and engine life. Cooling system problemsmay include small annoying leaks, fuel economy complaints,accelerated engine wear, or sudden catastrophic engine failure. If theflow of coolant in the engine stops for even a short amount of time,there is a high risk of significant damage to the engine.

Fig. 4.1.1 Cooling System and Energy Distribution

The cooling of an engine depends on the principles of conduction,convection, and radiation of heat energy in order to keep the enginerunning at the proper operating temperature. The coolant receives theheat that is conducted to it from the metal components of the engine;the engine block, the cylinder head, etc. The coolant is then forcedby the water pump from the engine to the radiator. At the radiator theheat energy is transferred by convection to the air moving across thefins of the radiator. In addition the engine also radiates a certainamount of energy to the atmosphere directly in the form of heat thatis given off from the engine to the surrounding air.

The components of a cooling system for an engine are extremelysimplistic. The basic components of every cooling system include:

The water jacket

The water temperature regulator(s) (thermostat(s))

The radiator (or heat exchanger)

The pressure cap

The water pump

Hoses

The engine may also have some type of coolant cooled aftercooler,oil cooler, hydraulic cooler, or transmission cooler.

Some marine or stationary systems may have a heat exchanger inplace of the radiator.

The pump is what causes the coolant to flow in the cooling system.Inside the engine are coolant passages that the water flows in. Thesepassages include what is sometimes called a "water jacket." Thewater jacket is the large cavity in the block and the head thatsurrounds the cylinders of the engine. This cavity is normally full ofcoolant and is what keeps the engine at a uniform temperature.

Fig. 4.1.2 Water Temperature Regulator

The water temperature regulator(s) (thermostat(s)) regulate the flowof coolant to the radiator. When the engine is cold, the watertemperature regulator is closed and the water coming from the engineis closed off from the radiator. The water is then recirculated throughthe water pump, back into the engine. This helps the engine acheiveoperating temperature more quickly. When the engine is warm, thewater temperature regulator allows the coolant to flow to the radiatorto be cooled before reentering the engine. The water temperatureregulator is not strictly fully open or fully closed. The watertemperature regulator modulates between open and closed in order tokeep a constant temperature in the engine. Proper engine temperatureis very important. An engine that runs too cold will not operate at ahigh enough temperature to have efficient combustion and will leadto sludge buildup in the lubrication system of the engine. An enginethat runs too hot will overheat and may lead to serious damage of theengine.

Fig. 4.1.4 Pressure Cap

Perhaps the most overlooked component of the cooling system is thepressure cap. The pressure cap has a relief valve that will not allowthe pressure of the cooling system to exceed a predetermined level.The pressure cap maintains a certain amount of pressure in thecooling system. This is very important because, by increasing thepressure of the cooling system by 1 psi, the boiling point of thecoolant is raised 3.25 degrees F. This allows coolant to run hotterwihout boiling. A typical cooling system will have anywhere from a7 psi to a 12 psi pressure cap, so this can have a significant effect onthe cooling of an engine.

Fig. 4.1.3 Radiator

The radiator is the component of the cooling system that rejects theheat from the coolant to the air. A radiator has tubes that the coolantflows through most generally from the top of the radiator to thebottom. At the bottom of the radiator there is a hose leading to thepump to start the circulation over again. The tubes have fins attachedto them that help to reject the heat to the air moving across theradiator.

Lesson 2: Remove and Install Cooling System Components

Les

son

2: R

emov

e an

d In

stal

l Coo

ling

Syst

em C

ompo

nent

s

Objectives:

Using the appropriate Caterpillar 3404 Service Manual, the studentwill demonstrate the ability to correctly remove, inspect, and installcooling system components.

References:

3406B Service Manual SEBR05443406C Service Manual SEBR0550

Introduction:

To effectively perform diagnosis, repair, and service on a dieselengine cooling system, it is necessary to be able to remove, inspect,and install the related components.

Lab Exercises

Using a lab engine or engine installed in a vehicle, show studentscooling system components and explain their function includingcoolant pump, regulator, and radiator. Test radiator cap using 9S8140Pressurizing Group. Test coolant using 8T5296 Coolant Test Kit.

Using a lab tear-down engine, remove water pump and discuss failuremode (bad seal, loose, eroded, or cracked impeller).

Remove temperature regulator (thermostat). Point out importance ofthe seal around the thermostat and trace flow of the bypass circuit.

Unit 4 4-2-2 Engine FundamentalsLesson 2

UNIT 5Diesel Fuel CharacteristicsMechanically Controlled Fuel Systems

Uni

t 5:

Die

sel F

uel

Unit Objectives:

1. The student will be able to explain the characteristics of dieselfuel and proper fuel system maintenance procedures forCaterpillar engines.

2. The student will be able to identify and explain the operation ofthe following Caterpillar fuel systems:new scroll,sleeve metering, andmechanical unit injector.

3. The student will be able to remove and install 3406 New ScrollFuel System, plunger and barrel group, nozzles, timing advance,and injection pump and governor group. The student willdemonstrate the ability to test a fuel nozzle.

Unit References:

Diesel Fuels and Your Engine SEBD07173406E Operation and Maintenance Manual SEBU6758Fuel Contamination Control PEHP7046Caterpillar New Scroll Fuel System Introduction CD-ROMUsing 5P4150 Nozzle Tester Group SEHS7292Testing 7000 Series Nozzles SEHS90833406B Service Manual SEBR05443406C Service Manual SEBR0550

Unit References: (Continued)

Fuel Nozzle Testing LEVP9167The Sleeve Metering Fuel System LEBQ9802The Sleeve Metering Fuel System CD-ROM LERV98023116/26 Mechanical Unit Injector Presentation CD-ROMUnit 5 Quiz

Tooling:

8T0461 Serviceman's Tool Set or equivalent6V4186 Pin9S9082 Turning Tool1P7408 Thermo-hydrometer5P5195 Fuel Line Wrench5P0144 Fuel Line Socket8S2244 Extractor8T5287 Wrench5P4150 Nozzle Test Group6V2170 Tube Assembly6V2171 Tube Assembly5P7448 Adapter8T3139 Spanner Wrench8T3198 Nozzle Tube8T3199 Nozzle Screw6V6983 Adapter1B4206 Nut8S2270 Collector Assembly6V4089 Nozzle Reamer6V7025 Nozzle Seal Guide1U9725 Nozzle Adapter Wrench

Lesson 1: Diesel Fuel

Les

son

1: D

iese

l Fue

l

Objectives:

The student will be able to explain diesel fuel characteristics andrelated maintenance.

References:

Diesel Fuels and Your Engine SEBD07173406E Operation and Maintenance Manual SEBU6758Fuel Contamination Control PEHP7046

Introduction:

Diesel fuel is by far the largest expense related to owning andoperating a diesel engine. The characteristics, quality, and handlingof the fuel affect the performance and life of the engine.

HEAT VALUE PER GALLONIN BTU

1D Diesel 137,0002D Diesel 141,800Gasoline 125,000Butane 103,000Propane 93,000

Fig. 5.1.1 Heating values of various fuels

The heating value of a fuel is defined as the amount of heat producedby burning a specific weight of fuel. This is an indicator of howmuch available energy is available in a specific amount of fuel. Thechart above shows the heating values for various common fuels. 1Ddiesel is winter blended diesel, and 2D diesel is summer blendeddiesel. Notice that both blends of diesel fuel have a significantlyhigher heating value than any of the other fuels listed. What thismeans is that in a given amount of diesel fuel there is more energyavailable to be turned into useful work. This is one of the significantadvantages to using diesel power as a source of energy.

Heating Value of Diesel Fuel

Lesson 2: Caterpillar 3406 New Scroll Fuel System

Les

son

2: C

ater

pilla

r34

06 N

ew S

crol

l Fue

l Sys

tem

Objectives:

The student will be able to explain the operation of the CaterpillarNew Scroll Fuel System.

References:

Caterpillar New Scroll Fuel System Introduction CD-ROM

Introduction:

The Caterpillar New Scroll Fuel System has been in production since1980 on the 3300 series engines. When the 3406B was released in1983, the New Scroll Fuel System was added to help improveemissions, performance, and fuel economy. Another benefit of theNew Scroll Fuel System is that the individual injection pumps do notneed adjustment or calibration.

Fig. 5.2.1 Caterpillar 3406B Engine

Caterpillar 3406B Engine

The Caterpillar 3406A was introduced in 1973. Since then, a numberof changes have been made to meet the demand for an even morereliable and economical product, while meeting governmentalregulations. The 3406B, released in 1983, is an example of thesechanges. The major change to this engine was the fuel system. TheNew Scroll Fuel System had been in production since 1980 on the3300 engines. This fuel system is a key factor in the emissions,performance and fuel economy improvements in the 3406B. In 1991,the fuel system was changed to incorporate a more aggressive fuelcamshaft to improve emissions. In 1992 the 3406C was introduced.There were no changes to the mechanical fuel system.

This presentation covers the Caterpillar New Scroll Fuel System.

Fig. 5.2.2

Caterpillar 3406 Fuel Injection Pump Groups

In the top view we can see how the 3406A Engine Fuel InjectionPump had a long drive because there wasnt room for the pumphousing under the air compressor. In the lower view we see the3406B/C Fuel Injection Pump. It is shorter, but more massive. Theshorter length of the 3406B/C pump leaves more room for servicing.

Fig. 5.2.3 Injection Pump Camshafts

Injection Pump Camshafts

Many of the changes and improvements were internal, and cant beseen. Here we see the fuel injection pump camshafts. The 3406A isat the top. The 3406B camshaft below it is larger and heavier, and isdriven by a gear on the left end. The 3406B cams have a differentconfiguration--they have a faster lift and shorter duration, increasingfuel injection pressures and reducing the time of injection, for greaterfuel efficiency. An eccentric on the camshaft operates the piston-typefuel transfer pump. With the changes for emissions in 1988, the noseof the camshaft changed. The 10 degrees helix on the front waschanged to a 15 degrees helix and the hole in the front was enlargedto accommodate a different timing advance unit. The emissionchanges for 1991 was a bearing diameter and lobe shape change only.

Fig. 5.2.4 3406 Fuel Flow

This is a schematic of the 3406B/C engine fuel system. Well use theschematic to follow the flow of fuel from the supply tank to theinjector in the cylinder. The transfer pump (5) pulls fuel from thefuel tank (1) through the supply shutoff valve (3) through the primaryfuel filter (4) to the fuel transfer pump itself. The transfer pump thenpressurizes the fuel and pushes it though the hand priming pump (7),into the secondary fuel filter (6) and into the fuel manifold (8) undermoderate pressure. A bypass valve inside the fuel transfer pumpmaintains moderate fuel pressure. With moderate fuel pressure insidethe fuel manifold and the void (vacuum) inside the high pressurepumps, the fuel is loaded into the cavity of the high pressure pump.The high pressure pumps now meter a small amount of fuel and sendsit though the high pressure fuel lines (9) and through the head adapter(10) to the injection nozzle (11) at a very high pressure. When thefuel pressure in the high pressure fuel lines gets above the nozzleopening pressure the fuel is injected into the combustion chamber.With both very high pressure and very small holes in the tip of thenozzle, the fuel is atomized and gives complete combustion in thecylinder. Any air and some fuel is sent out of the fuel manifoldthrough the return line (15) back to the supply tank. The tank drain(2) is used to remove water, sediment and foreign material and todrain the supply tank. The fuel tank cap (16) must be vented toatmosphere to keep vacuum from forming inside the fuel tank.

Fig. 5.2.5 3306 Fuel Flow

3306 Fuel Flow

This is a schematic of the 3306B/C engine fuel system. Well use theschematic to follow the flow of fuel from the supply tank to injectionin the cylinder. The transfer pump (6) pulls fuel from the fuel tank(9) through the supply shut off valve (3) through the primary fuelfilter (4) through the hand priming pump (5) into the transfer pumpitself. The transfer pump then pressurizes the fuel and pushes itthrough the secondary fuel filter (7) and to the fuel manifold in theinjection pump housing (8). A bypass valve inside the fuel transferpump maintains moderate fuel pressure. With moderate fuel pressureinside the fuel manifold and the void (vacuum) inside the highpressure pumps, the fuel is loaded into the cavity of the high pressurepump. The high pressure pumps now meter a small amount of fueland sends it though the external high pressure fuel lines (9) at a veryhigh pressure to the fuel injection nozzle (10). When the fuelpressure in the high pressure fuel lines gets above the nozzle openingpressure the fuel is injected into the combustion chamber. With bothvery high pressure and very small holes in the tip of the nozzle, thefuel is atomized and gives complete combustion in the cylinder. Aconstant bleed valve (11) lets a constant flow of fuel go through thefuel return line (12) back to the fuel tank (1). This helps keep thefuel cool and free of air. There is also a manual bleed valve that canbe used when the fuel priming pump is used to remove air from thesystem. The supply tank drain (2) is used to remove water, sediment,foreign material and to drain the supply tank. The fuel cap must bevented to atmosphere to keep a vacuum from forming inside the fueltank.

Fuel System Components

In this view we can see some of the components of the 3406B fuelinjection system on the engine. Visible are the fuel injection pumphousing, the governor housing, the fuel transfer pump and theexternal fuel injection lines.

Fig. 5.2.6 Fuel System Components

Fig. 5.2.7 3306 Fuel System Components

3306 Fuel System Components

In this view we can see some of the components of the 3306B/C fuelinjection system on the engine. Visible are the fuel injection pumphousing, the governor housing, the fuel transfer pump, fuel injectionlines, the fuel filter and base and the fuel priming pump.

Fig. 5.2.8 Fuel Transfer Pump

Fuel Transfer Pump

The fuel transfer pump is located on the bottom of the 3406B/C pumphousing and on the side of the 3304B or 3306B/C pump housing. Itis activated by the eccentric on the fuel pump camshaft inside thehousing and can deliver up to 51 gallons of fuel per hour at 25 psi.This is a spring pumping piston type pump where actual fuel pressureon the engine may vary from 20-45 psi depending on engineoperating conditions. The pump only supplies what the enginerequires, plus the amount returned to tank. (About 9 gallons perhour). It is a single piston, single action pump with three one-waycheck valves. The check valves are: inlet, pumping and outlet. Thisdrawing shows that pumping and fill occur on the same pump stroke.Here, the tappet is almost completely extended and the return springhas forced the piston to the top of the pump. This upward motion ofthe piston opens the inlet check valve and fuel enters the inlet cavity(green). The pumping check valve at the top of the piston is closedand the piston pushes fuel into the outlet cavity (red). Thispressurized fuel opens the outlet check valve at the outlet port. Thereis no pressure relief valve in this pump because fuel outlet pressure iscontrolled by the force of the piston spring.

Fig. 5.2.9 3406 Injection Pump

Fig. 5.2.10 3306 Injection Pump

3306 Injection Pump

This is a cutaway of a similar area of the 3306B/C fuel pump. Noticethe similarity of the two different pumps.

3406 Injection Pump

The area shown in red is the fuel gallery of the 3406B/C fuel pump.This area is pressurized by the fuel transfer pump. The cutawayshows the placement of the pump groups within the pump housing.Fuel enters and leaves the pump group by way of the hardenedhollow dowel. This dowel is in the housing to protect it from erosioncaused by the high pressure spill pulses.

Fig. 5.2.11 3406 Fuel Rack

Fig. 5.2.12 Fuel Metering

Fuel Metering

Well use a cutaway pump to see how fuel is metered and deliveredto the fuel injection nozzles. This is a scroll type fuel system with aleft-hand cut scroll on the pump plunger. The gear on the bottom ofthe plunger is engaged into the rack. Rack movement rotates theplunger in the pump barrel and changes the relationship of the scrollto the spill port (arrow). The camshaft/follower/lifter mechanismmoves the plunger up and down in the barrel. In this position, theplunger is at the bottom of its stroke. Fuel is coming into the barrelthrough the spill port in the back side of the barrel and through thefill port.

3406 Fuel Rack

The area shown in the slide is a cutaway of the engine side of the3406B/C fuel pump housing. This cutaway shows a complete pumpin the center and a cutaway pump on the right. We can see therelationship of the pump groups and the rack as the gear segmentengages the rack. Also note the lifters and return springs.

Fig. 5.2.13 Fuel Delivery

Fig. 5.2.14 End of Fuel Delivery

End of Fuel Delivery

At the end of the effective stroke, the spill port is opened by thescroll, fuel pressure is released and the reverse flow check valvecloses. During the entire pumping cycle the groove on the plunger ispositioned over the bleed back passage.

Fuel Delivery

Now, the cam has lifted the plunger so the fill port and spill port arejust closed. This is the start of the effective stroke of the plunger andthe beginning of injection. As the fuel in the barrel is pressurized, thereverse flow check valve is lifted off its seat in the pump bonnet.This sends pressurized fuel through the fuel lines to the injectionnozzle. Injection continues until the end of the effective stroke, whenthe scroll in the plunger lines up with the spill port in the barrel.

Fig. 5.2.15 Bleed Passage

Fig. 5.2.16 Reverse Flow Check Valve

Reverse Flow Check Valve

The reverse flow check valve keeps the fuel injection line full of fuelbetween injection strokes. Pressurized fuel (approximately 1000 psi)is kept in the injection line, ready for the next pump stroke. Whenthe engine and injection pump are stopped, the groove (arrow) bleedsthe pressure in the injection line to equalize with the residual pressurein the pump.

Bleed Passage

When the groove in the plunger is in this position, it is aligned withthe pressure bleed back passage in the barrel. This bleeds of fuelthat goes between the barrel and the plunger and prevents fueldilution in the engine oil.

Fig. 5.2.17 Reverse Flow Check Valve Operation

Fig. 5.2.18 Reverse Flow Check Valve

Reverse Flow Check Valve

Pressurization continues until the scroll opens the spill port and thepressure in the pump barrel is released. This seats the check valve,but the pressurized fuel in the injection line opens the return flowcheck valve. Fuel will return to the pump barrel and flow out thespill port until pressure in the injection line drops to 1000 psi. At thatpoint, the return flow check valve spring will seat the valve. Whenthe engine is shut off, a small groove in the face of the check valveallows the 1000 psi pressure to bleed off.

Reverse Flow Check Valve Operation

When fuel pressure in the barrel above the plunger reaches 100 psi,the valve is lifted off its seat and fuel flows out the cavity through thebonnet to the injection line. The check valve spring keeps the valveseated when fuel is at transfer pump pressure. This means that fuelcan enter the injections lines only during the injection stroke, helpingto eliminate cylinder wash down if an injection nozzle is stuck open.

Fig. 5.2.19 3406 Fuel Manifold Cover

Fig. 5.2.20 3306 Fuel Manifold Cover

3306 Fuel Manifold Cover

On the 3300 series engines, a spring steel pulse deflector is providedin the fuel manifold. This protects the aluminum manifold coverfrom the force of the released fuel pressure pulses.

3406 Fuel Manifold Cover

The high pressure fuel that exits through the spill ports goes throughthe hollow dowel into the fuel manifold and hits the cover plate.These highly pressurized fuel pressure pulses cause polish spots thatare lined up with the spill ports on the manifold cover plate of the3406B/C fuel system.

Fig. 5.2.21 Governor Operation


Governor Operation

The flyweights swing out as rpm increases. This moves the riser tocompress the governor spring and the pivoting lever moves the sleeveand spool toward the "fuel off" direction.

Governor Operation

At the point the rack screw (green) first comes in full contact with thetorque spring, the rack is at full load point (rated). As demandhorsepower increased, with the rack at rated position, the enginespeed decreases as the engine goes into lug (full throttle with rpm lessthan rated rpm). Depending upon the rigidity of the torque spring, atsome point, the governor spring causes the rack screw to begin todepress the torque spring. As this occurs, the rack position increasesallowing more fuel to be injected per stroke. This increase in rackposition continues until the torque screw (violet) contacts the stop lar.This is the full torque position of the rack.

Fig. 5.2.23 Valve Spool - "Fuel Off"


Governor Operation

If the engine were to slow down, the flyweights would swing inwhich would move the riser away from the governor spring and thepivoting lever moves the sleeve and spool toward the "fuel on"direction.

Valve Spool - "Fuel Off"

As the valve spool moves in the direction shown, a passage in thepiston opens and allows pressurized oil to enter the chamber behindthe piston. At the same time, the spool closes the passage behind thischamber. The pressurized oil forces the piston and rack toward the"fuel off" position. With no load on the engine, the rack will moveuntil the low idle setting is reached. This setting is determined by theamount of force put on the governor spring by the throttle restingagainst the low idle stop screw.

Fig. 5.2.25 Valve Spool - "Fuel On"

Fig. 5.2.26 Valve Spool - Stabilized Fuel Position

Valve Spool - Stabilized Fuel Position

This drawing shows the balance point of the servo spool and piston.When flyweight force equals governor spring force, the valve spoolblocks the oil in the chamber behind the piston. Rack position doesnot change and engine rpm is constant.

Valve Spool - "Fuel On"This spool movement blocks the passage inthe piston and opens the drain passage behind the chamber. Nowpressurized oil forces the piston and the rack in the direction shown(fuel on) so fuel delivery is increased until the desired rpm isobtained. The back and forth movement of the rack in the "fuel off"direction and in the "fuel on" direction will continue until there is abalance between the governor spring force and the flyweight force.

Fig. 5.2.27 Fuel Ratio Control Function

Fig. 5.2.28 Fuel Ratio Control Operation

Fuel Ratio Control Operation

A stem extends out of the fuel ratio control. This stem fits in a notchin a lever which contacts the end of the rack in the servo valve. Airinlet pressure (boost) is sensed by a diaphragm in the control. Thisdiaphragm pushes against a spring and spool. The spool movementcontrols the oil flow which moves a piston connected to the stem.The stem is out of the way during startup, so full rack is available onall mechanical 3406s. The same is true of 3300s, but beginning withthe 1994 3306C truck engine, the stem is partially retracted duringstartup, but does not go to full retraction until the engine develops oilpressure.

Fuel Ratio Control Function

The fuel ratio control mounts on the rear of the governor housing. Itspurpose is to limit smoke and improve fuel economy during rapidacceleration. It does this by controlling rack movement in the fuelON direction until there is enough (boost pressure) to allow completecombustion in the cylinders. With the fuel ratio control properlyadjusted, it also minimizes the amount of soot in the engine.

Fig. 5.2.29 Fuel Ratio Control Operation

Fuel Ratio Control Operation

When boost is low, the stem is in the set (cocked) position and thelever limits rack movement in the fuel ON direction. As boostpressure increases, The stem extends and moves away from the leverand the rack can move to the left allowing more fuel to be suppliedby the injection pumps. When manifold pressures of approximatelyone-half rated boost or above is reached, full fuel rack travel isavailable. Thus. anytime there is sufficient boost, the stem of the fuelratio control is extended and does not control or affect the movementof the rack. This permits smooth, rapid acceleration but at a rate thatallows complete combustion and low emissions.

Fig. 5.2.30 Fuel Shutoff Solenoid

Fuel Shutoff Solenoid

A fuel shutoff solenoid is located on the rear of the governor. Thereare two types. One is energized to run, the other is energized to shutdown. The one shown is an energized to run solenoid. When theengines electrical system is energized (key on), the solenoid isactivated and it releases linkage to allow rack movement in anydirection (fuel on - fuel off). When the electrical system is shut off(key off), the solenoid is deactivated and movement of the rack isprevented in the fuel ON direction, causing the engine to shut down.A diode is connected between the two terminals of the solenoid. Thediode eliminates electric spikes (high voltage generated by the coil ofthe solenoid when it is de-energized) that might damage otherelectronic circuitry in the vehicle electrical system.

Lesson 3: Remove, Inspect and Install Fuel System Components

Les

son

3: R

emov

e, I

nspe

ct a

nd I

nsta

ll F

uel

Syst

em C

ompo

nent

s

Objectives:

The student will demonstrate the ability to correctly remove andinstall 3406 fuel system components and test a nozzle.

References:

3406B Service Manual SEBR05443406C Service Manual SEBR0550Test Sequence for Caterpillar 7000 Series Fuel Nozzles SEHS9083Fuel Nozzle Testing LEVN9167

Introduction:

The Caterpillar 3406 fuel system normally requires very littleadjustment during the life of the engine. Normal maintenance mayrequire replacement of components such as filters, nozzles, andtransfer pump. Fuel system repairs may involve removal of plungerand barrel groups from the fuel injection pump, repair of the timingadvance, or removal of the complete fuel system from the engine.

Lesson 4: Sleeve Metering Fuel System

Les

son

4: S

leev

e M

eter

ing

Fue

l Sys

tem

Objectives:

The student will be able to explain how the Sleeve Metering FuelSystem operates.

References:

The Sleeve Metering Fuel System LEBQ98023208 Sleeve Metering Fuel System CD-ROM LERV9802Diesel Fundamentals and Service - Thiessen, Dales Textbook

Introduction:

The Caterpillar Sleeve Metering Fuel System was most recently usedon the 3208 engine. The 3208 was a popular mid-range on-highwaytruck engine until 1991 and saw continued use in marine andindustrial applications for many more years.

Lesson 5: 3116/26 Mechanical Unit InjectorFuel System

Les

son

5: 3

116/

26 M

echa

nica

l Uni

t In

ject

orF

uel S

yste

m

Objectives:

The student will be able to explain how the Mechanical Unit InjectorFuel System works.

Lesson 5 References:

3116/26 Mechanical Unit Injector Presentation CD-ROM

Introduction:

The Mechanical Unit Injector fuel system provides improvements inperformance and emissions when compared to some pump and linefuel systems. Caterpillar has used the Mechanical Unit Injector insmall engines such as the 3116/3126 and large engines such as the3500 and 3600 series.

Tooling: None

Fig. 5.5.1 1.1/1/2 Liter Engine Fuel Flow

1.1/1.2 Liter Engine Fuel Flow

The 1.1 liter engine fuel system utilizes a mechanical unit injectorcombining both the nozzle assembly and the high pressure fuelinjection pump. The fuel transfer pump) pulls fuel from the fuel tankthrough an in-line primary filter and sends fuel to a spin-on typesecondary fuel filter. From the fuel filter, fuel enters a drilled passageat the rear of the cylinder head. The drilled passage carries fuel to agallery around each unit injector and provides a continuous flow offuel to all of the unit injectors. Unused fuel exits the cylinder head,passes through a 1.3 mm (.050 in.) pressure regulating orifice and acheck valve and returns to the fuel tank. This system is very compactand eliminates external high pressure fuel lines. Additionally, thissystem allows very high injection pressures and short injection timesto aid exhaust emission control.

Introduction:

This presentation covers the Mechanical Unit Injector Fuel Systemused in the Caterpillar 3116/26 engine.

Fig. 5.5.2 Unit Injector

Fig. 5.5.3 Unit Injector Cut-away

Unit Injector Cut-away

The large extension on the side of the injector is the hold-downclamp. Shown at the bottom of the injector cut-away is the rack. Itsmovement controls the rotation of the helix on the scroll of theplunger, thus determining the volume of fuel to be injected into thecylinder. The unit injector consists of a scroll-type high pressureplunger and injector nozzle. Effective stroke of the plunger, duringwhich high pressure fuel is injected, is controlled by the scrollposition which is actuated by the governor and rack.

Unit Injector

The fuel injection system for this engine is a mechanical unit injectortype. The fuel injection pump and nozzle are combined in oneinjector assembly for each cylinder. All high pressure lines areeliminated. Fuel lines consist of supply lines to and from the cylinderhead, fuel filter and fuel transfer pump. Fuel is supplied to eachinjector by an internal passage running the full length of the head.Each unit injector has its own fuel rack

Basic Engine(the Best)

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