5.4" BORE, V12 VEHICULAR ENGINE Caterpillar


Systems Operation

Usage:



Introduction

NOTE: For Specifications with illustrations, make reference to SPECIFICATIONS FOR 5.4" BORE, 60° V12 VEHICULAR ENGINE, Form No. REG01561. If the Specifications in Form REG01561 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications in the book with the latest date.

Fuel System


FUEL SYSTEM SCHEMATIC
1. Bleed valve. 2. Fuel injection pump. 3. Bleed manifold. 4. Fuel manifold. 5. Precombustion chamber. 6. Fuel transfer pump bypass valve. 7. Priming pump. 8. Bleed valve. 9. Fuel tank. 10. Primary fuel filter. 11. Fuel transfer pump. 12. Fuel filters.

Fuel is drawn from the fuel tank through the primary fuel filter (10) by the transfer pump (11). This pump is mounted on the fuel filter housing and is driven by a shaft connected to the fuel injection pump camshaft.

A bypass valve (6) at the inlet side of the fuel filter assures adequate pressure for the fuel system and allows excess fuel to be bypassed back to the fuel tank (9) through a return line.

A fuel priming pump (7) is used to fill the filter case, pressurize the fuel and assure that the system is free of air prior to starting the engine. A system of check valves allows fuel to be pumped past the fuel transfer pump when the priming pump is in use. As the filter (12) and fuel injection pump (2) passages are being filled with fuel from the priming pump, bleed valve (8) on the filter housing can be opened to allow air to escape. The bleed valve (1) on the fuel manifold can be used to allow any entrained air to escape from the individual fuel pumps and eliminate the need for loosening fuel line connections at the individual fuel pumps.

Individual fuel injection lines carry fuel from the pumps to each cylinder. One section of line connects between the fuel injection pump and an adapter on the inward portion of the camshaft housing. Another section of line on the inside of the camshaft housing connects between the adapter and the top of the precombustion chamber.

The fuel pump camshaft is driven by gears located inside a cover at the rear of the engine. An adjustable drive gear at the rear of the engine vee, drives a speed sensing, variable timing unit which in turn is coupled to the fuel pump camshaft through a sliding spline. This variable timing unit automatically provides retarded timing for easier starting and smooth low rpm operation. It will also advance timing as engine rpm increases to provide optimum engine operating efficiency.

Fuel Injection Pump

Fuel enters the fuel injection pump housing through passage (6) and enters the fuel injection pump body through the inlet port (2). The injection pump plungers (5) and the lifters (11) are lifted by the cam lobes (12) on the camshaft and always make a full stroke. The lifters are held against the cam lobes by the springs (3). Each pump measures the amount of fuel to be injected into its respective cylinder and forces it out the fuel injection nozzle.


FUEL INJECTION PUMP
1. Check valve. 2. Inlet port. 3. Spring. 4. Lubrication passage (fuel). 5. Pump plunger. 6. Fuel passage. 7. Bleed passage. 8. Fuel rack. 9. Lubrication passage (oil). 10. Gear segment. 11. Pump Lifter. 12. Camshaft lobe.

The amount of fuel pumped each stroke is varied by turning the plunger in the barrel. The plunger is turned by the governor action through the fuel rack (8) which turns the gear segment (10) on the bottom of the pump plunger. Passage (4) provides fuel to lubricate the pump plunger and passage (7) allows air to be bled from the system through the valve on top of the fuel filter case.

Fuel Injection Valve

Fuel, under high pressure from the injection pumps, is transferred through the injection lines to the injection valves. As high pressure fuel enters the nozzle assembly, the check valve within the nozzle opens and permits the fuel to enter the precombustion chamber. The injection valve provides the proper spray pattern.


FUEL INJECTION VALVE CROSS SECTION
1. Fuel line assembly. 2. Seal. 3. Body. 4. Nut. 5. Seal. 6. Nozzle assembly. 7. Glow plug. 8. Precombustion chamber.

Speed Sensing, Variable Timing Unit

The variable timing unit, couples the fuel injection pump camshaft to the engine rear timing gears. The variable timing unit advances the timing as engine rpm increases.

On earlier engines the timing advances from 11° BTC at low idle to 19° BTC at high idle. On later engines the timing advances from 8° BTC at low idle to 19° BTC at high idle.


LOW RPM POSITION
1. Power piston. 2. Power piston cavity. 3. Control valve spring. 4. Power piston return spring. 5. Oil inlet passage. 6. Drain port. 7. Control valve. 8. Flyweights. 9. Shaft assembly.

During engine low rpm operation, the flyweight (8) force is not sufficient to overcome the force of control valve spring (3) and move control valve (7) to the closed position. Oil merely flows through the power piston cavity (2).

As the engine rpm increases, flyweights (8) overcome the force of control valve spring (3) and move control valve (7) to the closed position, blocking the oil drain port (6). Pressurized oil, trapped in power piston cavity (2), overcomes the force of spring (4) and moves power piston (1) outward. This causes the fuel injection pump camshaft to index slightly ahead of the shaft portion (9) of the variable timing unit. Any outward movement of the power piston increases the force on the control valve spring. This tends to reopen the control valve, letting oil escape from the power piston cavity. As oil begins flowing from the cavity again, return spring (4) moves the power piston inward.


HIGH RPM POSITION
1. Power piston. 2. Power piston cavity. 3. Control valve spring. 4. Power piston return spring. 5. Oil inlet passage. 6. Drain port. 7. Control valve. 8. Flyweights. 9. Shaft assembly.

At any given rpm, a balance is reached between the flyweight force and the control valve spring force. The resultant position of control valve (7) will tend to maintain proper pressure behind the power piston. The greater the rpm, the smaller the drain port opening, and the further outward the power piston is forced.

As the power piston is moved outward, the angular relationship of the ends of the drive unit change. As the power piston moves forward in the internal helical spline, the fuel injection pump timing advances.

The gear teeth on shaft assembly (9) drive the governor drive pinion.

Governor


GOVERNOR CROSS SECTION (Typical Example)
1. Adjusting screw. 2. Collar. 3. Shutoff shaft. 4. Stop bar. 5. Lever assembly. 6. Bolt. 7. Governor spring. 8. Seat assembly. 9. Flyweights. 10. Seat. 11. Valve. 12. Cylinder. 13. Oil passage. 14. Piston and valve assembly. 15. Sleeve. 16. Gear. 17. Body assembly. 18. Shaft. 19. Shaft assembly. 20. Lever. 21. Quill shaft. 22. Drive pinion. 23. Fuel rack. A. Speed limiter (Machines so equipped).

An oil pump gear (16), part of shaft (19), provides immediate pressure oil for the servo portion of the governor. A sump in assembly (17) provides immediate supply for the pump. A bypass valve, in the body assembly, maintains correct pressure for servo supply oil.

When the engine is operating, pressure oil from the pump is directed through passage (13) in cylinder (12), to a space around sleeve (15) and through an oil passage in piston (14) to a groove around valve (11). When revolving weights (9) slow down (occurring when engine load increases), the weights move in allowing governor spring (7) to move valve (11) downward. When the valve moves downward, the oil passage in piston (14) opens to the pressure oil in the groove around valve (11) and pressure oil is now at the large area end of piston (14) and pushes the piston, valve (11) and shaft (18) downward. Shaft (18) pushes lever (20), moving the fuel rack (23) forward thus increasing the amount of fuel to the engine.

With more fuel, engine rpm increases until the revolving weights again rotate fast enough to balance the force of the governor spring. The passage in piston (14) will be between the oil pressure groove and the oil drain groove in valve (11). The movement of piston (14), valve (11), shaft (18), lever (20) and fuel rack (23) stops and the engine rpm is the same as before. When engine load decreases, revolving weights (9) speed up and toes on the weights move valve (11) upward opening oil passage in piston (14) to the drain groove around valve (11). Oil pressure between sleeve (15) and piston (14) pushes the piston, valve (11) and shaft (18) upward which moves fuel rack (23) to decrease the amount of fuel to the engine and the rpm of the engine (and revolving weights) decreases. When revolving weight force again balances governor spring force, the rpm of the engine is the same as before.

An oil passage through the center of valve (11) has a small oil outlet near the top end of the valve to lubricate a thrust bearing under seat (10). The bearing surface of revolving weight assembly (9) drive gear receives lubricating oil from the oil around sleeve (15) through an opening in cylinder (12).

Governor action will change if there is a loss in lubricating oil pressure; however, the governor still offers protection against engine overspeeding because the weight assembly is mechanically connected to the fuel rack. The mechanical connections make it possible to move the fuel rack to the SHUTOFF position by using the controls normally used to stop the engine.

On the 992 (25K), the operator stops the engine by pulling up on the accelerator pedal until the control lever on the governor goes past the detent between low idle and stop positions.

On the 776 Tractor, 777 Truck and D348 Vehicular Engines, the operator stops the engine by the shutoff solenoid. On the 776 and 777, the push button switch which activates the shutoff solenoid is below the key operated battery disconnect switch. A manual shutoff lever is on the governor for emergency use.

When the engine is started, speed limiter plunger (A) restricts the movement of the governor control linkage. When operating oil pressure is reached, the plunger in the speed limiter retracts and the governor control can be moved to the HIGH IDLE position.

Fuel Ratio Control

The fuel ratio control coordinates the movement of the fuel rack with the amount of air available in the inlet manifold. The control keeps the air to fuel ratio more efficient, thus minimizing exhaust smoke.

A manually operated override lever (1) is provided to allow unrestricted rack movement during cold starts. After the engine starts, the override automatically resets in the RUN position.


FUEL RATIO CONTROL CROSS SECTION
1. Lever. 2. Housing. 3. Spring. 4. Spring. 5. Diaphragm. 6. Collar. 7. Bolt assembly.

Collar (6) mechanically connects to the fuel rack. The head of bolt assembly (7) latches through a slot in collar (6). An air line connects the chamber above diaphragm (5), with the air in the engine inlet manifold.

When the operator moves the governor control to increase engine rpm, the governor spring moves collar (6) down until it contacts the head of bolt assembly (7). The bolt assembly restricts the movement of the bolt and collar until spring (3) and the turbocharger boost of air pressure in housing (2) forces diaphragm (5), spring (4) and bolt assembly (7) to relieve the bolt head restriction to bolt and collar (6). This allows the fuel rack to move to increase the fuel as turbocharger air pressure (boost) increases with the increase in engine rpm.

Fuel Ratio Control (Hydraulic Activated)

The hydraulic activated fuel ratio control automatically causes a restriction to the amount of travel of the rack in the "fuel on" direction, until the air pressure in the inlet manifold is high enough to give complete combustion. The fuel ratio control keeps engine performance high.


FUEL RATIO CONTROL (HYDRAULIC ACTIVATED)
1. Valve. 2. Oil inlet passage. 3. Passage for inlet air pressure. 4. Oil outlet passage. 5. Large oil passage. 6. Oil drain. 7. Spring. 8. Diaphragm. 9. Valve.

The hydraulic activated fuel ratio control has two valves (1) and (9). Engine oil pressure works against valve (1) to control the movement of the fuel rack. Air pressure from the inlet manifold works against diaphragm (8) to move valve (9) to control oil pressure against valve (1).

When the engine is stopped, there is no pressure on either valve. Spring (7) moves both valves to the ends of their travel. In this position, the fuel rack travel is not restricted. Also in this position, an oil outlet passage (4) is open to let oil away from valve (1).

When the engine is started, the open oil outlet passage (4) prevents oil pressure against valve (1) until air pressure from the inlet manifold is high enough to move valve (9) to close the large oil passage (5). Engine oil pressure then works against valve (1) to move this valve into its operating position. The control will operate until the engine is stopped.

When the governor control is moved toward the full load position with the engine running, the head on the stem of valve (1) will cause a restriction to the travel of the fuel rack, until the air pressure in the inlet manifold has an increase. As there is an increase in the air pressure in the inlet manifold, this pressure works against diaphragm (8) to cause valve (9) to move to the left. The large oil passage (5) becomes open to let oil pressure away from valve (1), toward spring (7), and out to drain (6). As there is a decrease in oil pressure, valve (1) moves to the left to let the fuel rack open at a rate equal to (the same as) the air available for combustion.

Governor Control (For 776 And 777 Engines)

This engine has an air activated governor control. The operator's accelerator pedal is connected to an air valve. This air valve is connected by an air line to the slave cylinder. The slave cylinder is attached to the under side of the beam which is above the governor. The slave cylinder has a mechanical linkage to the governor control lever.

The air valve is a modulating valve. When the operator moves the accelerator pedal in either direction, the air valve opens either the inlet or exhaust port. If the pedal is pushed down for more speed or power, the air valve lets air into the line to the slave cylinder until the pressure in the line and the slave cylinder is correct for the position of the pedal. At that point the inlet port closes and the air is locked between the air valve and the slave cylinder. This keeps the governor control at that position until the operator moves the pedal either up or down.

When the pedal is released, the exhaust port is opened and the air pressure between the air valve and the slave cylinder is released until it is correct for the position of the pedal.

The slave cylinder has a piston which makes the air pressure work against a spring. The more air pressure, the more the spring is compressed and the farther the governor control lever is moved toward full speed. When the air pressure is released, the spring moves the piston back toward the low idle position. The combination of the forces of the air pressure and the spring work together to put the governor control in the correct position. The pressure in the system goes from 0 psi (0.0 kg/cm2) (0 kPa) to 60 psi (4.22 kg/cm2) (414 kPa) as the pedal is moved to change from low idle speed to high idle.

NOTE: The air reservoir must be filled with 60 psi (4.22 kg/cm2) (414 kPa) air to make the slave cylinder move all the way when the operator pushes on the pedal. If there is no air pressure in the air reservoir, the governor control lever must be moved manually to get the maximum amount of extra fuel for starting.

Air Induction And Exhaust System

Air Induction And Exhaust System For 992 Engine


AIR INDUCTION AND EXHAUST SCHEMATIC (Earlier Engines Illustrated)
1. Exhaust manifold. 2. Turbocharger. 3. Intake manifolds. 4. Air inlet. 5. Exhaust manifold. 6. Turbocharger.

Inlet air passes through an air cleaner assembly to a single inlet pipe. The air flow is divided and directed to the compressor section of each turbocharger. On earlier engines, compressed air from the right side turbocharger flows to the left side inlet manifold.

Compressed air from the left side turbocharger flows to the right side inlet manifold. This cross-blown arrangement provides balanced manifold pressures in each bank.

NOTE: On later engines, the cross blown arrangement has been replaced by an equalizer tube between the intake manifolds.

Air Induction And Exhaust System For 776 Tractor, 777 Truck, And D348 Vehicular Engines


AIR INDUCTION EXHAUST SCHEMATIC
1. Left side exhaust manifold. 2. Aftercoolers. 3. Right side exhaust manifold. 4. Equalizer tube. 5. Air inlet. 6. Turbocharger. 7. Exhaust outlet. 8. Turbocharger. 9. Air inlet.

This air induction and exhaust system has a turbocharger and an aftercooler for each bank of cylinders. The turbocharger for each bank is driven by the exhaust gases for that bank. The turbocharger pulls air through the air cleaner, into the compressor side of the turbocharger. The air is then pushed into the aftercooler housing. Air pressure in the two aftercooler housings is balanced by equalizer tube (4) which goes between the two housings. The air in the aftercooler housing is directed through the aftercooler cores. Coolant continuously passes through the aftercooler cores to cool the air before it goes into the combustion chamber. The cooled air is denser and is more efficient for combustion. The coolant can be engine coolant such as on some of the D348 Vehicular Engines. The coolant can also come from a separate circuit just for the aftercoolers. This type of system is found on the 776 Tractor, 777 Truck, and some D348 Vehicular Engines. These systems have separate coolant, piping, radiators and water pumps.

After the air has gone through the aftercooler core, it goes into the cylinders when the intake valves open. Here the cooled air is an advantage because it is more dense and has greater combustion efficiency.

There are four valves (two inlet and two exhaust) for each cylinder. The valves are actuated by overhead camshafts and forked rocker arm assemblies, located in the housing on top of the cylinder heads.

Exhaust gases leave each cylinder through two exhaust valve ports. After passing through the turbine side of the turbochargers, the exhaust exits through exhaust outlet (7) located between the turbochargers.

Turbochargers

The turbochargers are supported by brackets mounted to the engine cylinder block. All the exhaust gases from the diesel engine pass through the turbochargers.


TURBOCHARGER (Typical Illustration)
1. Air inlet. 2. Compressor housing. 3. Nut. 4. Compressor wheel. 5. Thrust plate. 6. Center housing. 7. Lubrication inlet port. 8. Shroud. 9. Turbine wheel and shaft. 10. Turbine housing. 11. Exhaust outlet. 12. Spacer. 13. Ring. 14. Seal. 15. Collar. 16. Lubrication outlet port. 17. Ring. 18. Bearing. 19. Ring.

The exhaust gases enter the turbine housing (10) and are directed through the blades of a turbine wheel (9), causing the turbine wheel and a compressor wheel (4) to rotate.

Filtered air from the air cleaners is drawn through the compressor housing air inlet (1) by the rotating compressor wheel. The air is compressed by action of the compressor wheel and forced to the inlet manifold of the engine.

When engine load increases, more fuel is injected into the engine cylinders. The volume of exhaust gas increases causing the turbocharger turbine wheel and compressor impeller to rotate faster. The increased rpm of the impeller increases the quantity of inlet air. As the turbocharger provides additional inlet air, more fuel can be burned; hence more horsepower derived from the engine.

Maximum rpm of the turbocharger is controlled by the rack setting, the high idle speed setting and the height above sea level at which the engine is operated.

------ WARNING! ------

If the high idle rpm or the rack setting is higher than given in the book RACK SETTING INFORMATION (for the height above sea level at which the engine is operated), there can be damage to engine or turbocharger parts.

--------WARNING!------

The bearings for the turbocharger use engine oil under pressure for lubrication. The oil comes in through the oil inlet port (7) and goes through passages in the center section for lubrication of the bearings. Oil from the turbocharger goes out through the oil outlet port (16) in the bottom of the center section and goes back to the engine lubricating system.

The fuel rack adjustment is done at the factory for a specific engine application. The governor housing and turbocharger are sealed to prevent changes in the adjustment of the rack and the high idle speed setting.

Cylinder Heads, Valves And Camshafts

Cylinder Heads and Valves

This is a four stroke cycle engine; i.e., four separate piston strokes are required to complete the firing of one cylinder.

There are four in-head valves for each cylinder; two intake valves and two exhaust valves.

The in-head valves are perpendicular to the bottom face of the cylinder head. The exhaust valves and ports are located toward the outside of the engine. The intake valves are on the inside, toward the vee.

A primary feature of the cylinder head is parallel porting. This provides individual porting for each of the two exhaust valves and the two intake valves. This permits unrestricted flow of air and exhaust gasses; resulting in maximum breathing capability and efficiency.

Valves, valve seats, seating springs and rotators are all part of the cylinder head assembly. The valve seats are pressed into the cylinder head and are replaceable.

Valve rotators add much to valve life. Each valve is rotated approximately three degrees on every lift; thus minimizing pitting of the valve faces and valve seats. The rotation also causes a wiping action to remove carbon deposits from the valve seat.

Rocker Arms

Valve action is accomplished through a roller-rocker arm arrangement. The forked rocker arm (2), located in the camshaft housing, pivots on a shaft (4) at one end and depresses two valves at the other end through adjusting screws. A roller (5), supported by a pin near the center of the rocker arm, rides on the camshaft (1) lobe. Thus, one camshaft lobe actuates the forked rocker arm and opens two valves simultaneously.


ROCKER ARM
1. Camshaft. 2. Rocker arm. 3. Adjusting screw. 4. Pivot shaft. 5. Roller. 6. Spring. 7. Valve.

Valve adjustment can be quickly and accurately accomplished with a screwdriver. No thickness gauge is required. Turn the adjusting screw (3) down to remove all clearance, then back off to the required setting.

Camshafts

This engine uses two overhead camshafts in each cylinder bank. The inner camshaft in each bank actuates all the intake valves and the other camshaft actuates all the exhaust valves.

The camshafts are driven from both ends of the engine. The right bank camshafts are driven by the rear gear train. On the left bank, the inlet camshaft drives the exhaust camshaft. On the right bank, the exhaust camshaft (F) drives the inlet camshaft (E).


CYLINDER BLOCK
A. Flywheel end. B. Left side. C. Front end. D. Right side. E. Inlet camshaft. F. Exhaust camshaft.

The camshaft journals are supported in integrally cast webs of the camshaft housings. Pressure lubrication to the camshaft journals is supplied from the cylinder block through the cylinder head, and into drilled passages in the camshaft housing.

A crankcase breather is mounted on the front of the right bank camshaft cover. The element is removable for cleaning. A fumes disposal tube carries the crankcase fumes to a level below the engine.

Lubrication System


LUBRICATION SYSTEM SCHEMATIC
1. Turbochargers. 2. Oil lines (turbocharger drain). 3. Oil passage (for valve mechanism on left side of engine). 4. Oil passage for governor and fuel injection pump housing). 5. Main oil manifold. 6. Oil passages to main bearings. 7. Oil passage (for valve mechanism on right side of engine). 8. Oil passage (to rear timing gears). 9. Oil passage (oil cooler to oil filters). 10. Oil filter bypass valve. 11. Oil cooler bypass valve. 12. Oil passage (to front timing gears). 13. Turbocharger lubrication valve. 14. Oil passage (from oil filters to engine components). 15. Oil cooler. 16. Oil filter base. 17. Oil lines to turbochargers. 18. Oil filters. 19. Scavenging oil pump. 20. Oil pump. 21. Oil pump bypass valve. 22. Oil pan (sump). 23. Oil line (scavenging pump suction). 24. Oil line (from oil pump to oil cooler and oil filters).

The flow of oil through the engine is as follows: oil from the oil pan (sump) (22) goes from the oil pump (20) through oil line (24) to oil cooler (15) and oil filters (18). Clean oil goes from the oil filters through oil passage (14) to the rear part of the engine to oil passage (8) for the lubrication of the rear timing gears. Oil passages (3) and (4) get their oil from oil passage (14). The valve mechanism on the left side of the engine gets its lubrication oil from the oil passage (3). The governor and fuel injection pump housing get lubrication oil from oil passage (4). Oil in passage (14) also goes to main oil manifold (5), oil passages (6, 7 and 12). The oil from oil passages (6) gives lubrication to the main bearings and connecting rod bearings. The piston cooling jets get their oil from oil passages (6). The valve mechanism on the right side of the engine gets lubrication oil from oil passage (7). The front timing gears get their oil from oil passage (12).

Bypass valve (21) is in the oil pump body. It controls the maximum oil pressure from the oil pump.

When the engine is started, the lubricating oil in the oil pan (sump) (22) is cold (cool). This (cool) oil opens oil filter bypass valve (10) and oil cooler bypass valve (11) to let oil flow immediately through the engine. The location of these valves (10 and 11), is in the oil filter base (16). The pressure of the (cool), oil in the oil passage (14) opens the turbocharger lubrication valve (13). The oil goes immediately through the valve and through oil lines (17) to turbochargers (1). When oil pressure through the oil cooler (15) and oil filters (18) is the same, the turbocharger lubrication valve (13) closes. Filtered oil is then sent to the turbochargers (1) through oil lines (17). As oil gets warm and pressure gets less, the oil filter bypass valve (10) closes. As the oil gets hot the oil cooler bypass valve (11) closes. Oil then goes through the oil cooler (15) to oil passage (9) and oil filters (18) before it goes to the engine components.

Dirt and restrictions in the oil filter elements will not stop lubricating oil from getting to the many parts of the engine. The oil filter bypass valve (10) will open, and let oil go around the oil filter elements.

The piston cooling jets in the cylinder block throw oil toward the bottom of the pistons for cooling and for lubrication of the piston pins, piston, piston rings and cylinder liner walls.

The connecting rod bearings get their oil from drilled passages in the crankshaft. When the engine is warm and running at rated speed, the oil pressure gauge must be in the "operating range." A lower pressure indication on the oil pressure gauge is normal at idling speed.

The scavenging oil pump (19) takes oil from the front of the oil pan and sends it through oil line (23) into the oil pan (sump) (22).

The governor gets lubrication from the passage (4). Lubrication oil for the governor goes from the governor to a sump in the bottom of the governor housing. An oil level is kept in the sump by an overflow pipe to give a supply of lubrication oil for the governor and the fuel injection pump housing. Lubrication oil goes from the governor housing sump through the overflow pipe into the fuel injection pump housing. Inside the governor is an oil pump. The governor oil pump takes oil from the sump in the bottom of the governor housing to give immediate lubrication to the servo mechanism. This immediate supply of oil to the servo mechanism will give immediate action of the governor when the engine is started.

The fuel injection pump has a manifold to supply lubrication oil to the bearings for the fuel injection pump camshaft and the lifter rollers. The lifter rollers and camshaft get oil each time a lifter is moved up and an oil hole is opened. Oil goes back to the engine cylinder block from the fuel injection pump housing.

Cooling System


SCHEMATIC OF THE COOLING SYSTEM
1. Expansion tank. 2. Shunt line. 3. Vent line from top tank to expansion tank. 4. Return line from regulator housing to radiator top tank. 5. Shunt line. 6. Top tank. 7. Engine oil cooler. 8. Line from water pump to engine oil cooler. 9. Cylinder head. 10. Passage from cylinder head to regulator housing. 11. Regulator housing. 12. Regulators (three). 13. Passage from cylinder head to regulator housing. 14. Vent tube from top of water pump to cylinder head. 15. Cylinder head. 16. Bypass line from regulator housing to water pump. 17. Core of radiator. 18. Bottom tank. 19. Water pump inlet line. 20. Valve for control of oil to fan drive. 21. Water pump. 22. Drain line from bottom of water pump to bypass line. 23. Line from water pump to torque converter oil cooler. 24. Oil cooler for the torque converter.

The radiator has an expansion tank (1), top tank (6), core (17) and bottom tank (18). Vent line (3) connects top tank (6) to expansion tank (1). The expansion tank has two shunt lines (2) and (5) that connect to the inlet of the water pump. The shunt lines keep a positive supply of coolant to the inlet of the water pump all of the time. When filling the cooling system, coolant from the expansion tank (1) will go through shunt lines (2) and (5) to the inlet of the water pump and fill the cooling system from the bottom. Air in the system is forced out through top tank (6) and through vent line (3) into the expansion tank (1). Vent tube (14) lets air in water pump go into the cylinder head when filling the cooling system. Drain line (22) will let all of the coolant out of the bottom of the water pump when the coolant is removed from the cooling system. The water temperature regulators (12) are located in the regulator housing (11) on the top front of the engine. Passages (10 and 13) connect the regulator housing to the cylinder heads. When the water temperature regulators are open, the bottom part of the regulator housing and the bypass line (16) are closed off and coolant from the cylinder heads (9) and (15) goes through the water temperature regulators (12) to the top of the regulator housing (11). The coolant goes from the regulator housing through return line (4) to top tank (6). The coolant goes from the top tank down through the core (17) of the radiator to bottom tank (18) and returns to water pump (21) through water pump inlet line (19). If the water temperature regulators (12) are not installed, not enough coolant will go through the core of the radiator and the coolant will get too hot.

When water temperature regulators (12) are closed, the top part of the regulator housing and the return line (4) are closed off. Coolant from the cylinder heads (9) and (15) goes through passages (10 and 13), through the center of water temperature regulators (12) to the bottom part of the regulator housing to bypass line (16) and returns to water pump (21).


FLOW OF COOLANT (SCHEMATIC) (Regulators open)
4. Return line to top tank.

The water pump (21) (centrifugal type) is mounted on the left front of the engine and is driven by the timing gears at the front of the engine. The water pump has two outlets.

Coolant from the upper outlet of water pump (21) goes through line (8) to the engine oil cooler (7). Coolant then goes through the oil cooler and into the right side of the cylinder block and to cylinder head (9). The coolant then goes from cylinder head through passage (10) to regulator housing (11).


FLOW OF COOLANT (SCHEMATIC) (Regulators closed)
16. Bypass line.

Coolant from the bottom outlet of the water pump (21) goes through line (23) to oil cooler (24) for the torque converter. Coolant then goes through oil cooler for the torque converter and into the left side of the cylinder block to cylinder head (15). The coolant then goes from cylinder head (15) through passage (13) to regulator housing (11).

Fan Drive

Fluid Coupling For Earlier 992 (25K)

Power for the 992 fan comes from the timing gears through a fluid coupling in the fan drive. When the temperature of the coolant in the inlet line to the water pump is 180°F (85°C) or more the charging valve supplies oil from the oil manifold in the block to the fan drive. On later machines this valve has been removed and engine oil is directly supplied to the fan drive.

The efficiency of the fluid coupling is dependent on the pressure and quantity of the oil supply. The oil supply should be at a temperature of 190° ± 10° F (188° ± 6° C) and with a minimum pressure of 45 psi (3.17 kg/cm2) (310 kPa).

With the correct oil supply to the fan drive, and the engine at 2000 rpm (full load speed) the fan speed must be 1500 ± 50 rpm.

NOTE: Allow at least five minutes with the engine at the correct speed for the fan speed to get to 1500 ± 50 rpm.

V-Belt Drive

Power for the fan comes from the crankshaft pulley through a set of V-belts.

Aftercooling Systems

Jacket Water Aftercooling Some D348 Engines


JACKET WATER AFTERCOOLING SCHEMATIC
1. Radiator. 2. Return line. 3. Bypass line. 4. Aftercooler outlet line. 5. Aftercoolers. 6. Fan. 7. Water pump. 8. Water pump supply line. 9. Supply line from water pump to engine oil cooler. 10. Aftercooler supply line from water pump.

Coolant is supplied to the water pump through line (8) from the radiator. Coolant flow is divided when leaving the water pump. Part of the coolant is directed through line (10) to the rear of the aftercoolers. Coolant from each aftercooler enters line (4) and is directed to the cylinder block.

The other stream of coolant from the water pump is directed through line (9) to the engine oil cooler and then into the cylinder block. The two streams of coolant join in the cylinder block. Coolant is then directed through the cylinder block and up through the cylinder head to the water temperature regulators, located at the front of the engine.

Until the coolant reaches the temperature required to open the temperature regulators, coolant is bypassed through line (3) back to the water pump. When the temperature regulators are open, coolant is directed to the radiator through line (2).

Separate Water Circuit Aftercooling All 776, 777, and some D348 Engines


SEPARATE WATER CIRCUIT AFTERCOOLING SCHEMATIC
1. Aftercooler radiator. 2. Return line. 3. Aftercoolers. 4. Fan. 5. Jacket water pump. 6. Engine. 7. Jacket water radiator. 8. Supply line to water pump. 9. Aftercooler water pump. 10. Supply line from water pump to aftercoolers.

Coolant for the aftercooling circuit is supplied from aftercooler radiator through line (2) to the gear driven aftercooler water pump, located on the left rear of the front timing gear housing. Coolant from the pump is directed through line (3), located on the left side of the cylinder block, to a tee connection at the rear of the engine where the coolant flow is divided equally and directed to the rear of each aftercooler. Coolant flows through the aftercoolers, combines into one line (1), and is directed to the top of the aftercooler radiator.

Basic Engine Components

Cylinder Block


CYLINDER BLOCK
A. Flywheel end. B. Left side. C. Front end. D. Right side.

The cylinder block is a 60° vee. One bank of cylinders is offset from the other bank of cylinders. This offset provides space at each end of the cylinder block for the camshaft drives. The offset also allows two connecting rods to be secured to each connecting rod journal of the crankshaft.

Cylinder Liners

On earlier engines a steel spacer plate is used between the cylinder heads and the cylinder block. The cylinder liners are supported in counterbores in the spacer plate.

On later engines the cylinder liner sits directly on the cylinder block. Engine coolant flows around the liners to cool them. Three O-ring seals at the bottom and a filler band at the top of each cylinder liner form a seal between the cylinder liner and the cylinder block.

Pistons, Rings And Connecting Rods

The piston has three rings; two compression rings and one oil ring. All rings are located above the piston pin bore. The two compression rings seat in an iron band which is cast integrally in the piston. The oil ring is spring loaded. Holes in the oil ring groove provide for the return of oil to the crankcase.

The full-floating piston pin is retained by two snap rings which fit in grooves in the pin bore.

A steel heat plug, in the crater of the piston, protects the top of the piston from erosion and burning at the point of highest heat concentration.

Oil spray jets, located on the cylinder block main bearing webs, direct oil to cool and lubricate the piston components and cylinder walls.

The connecting rods have diagonally cut serrated joints which allow removal of the piston and connecting rod assembly upward through the cylinder liner. Earlier engines use the same part number connecting rod for both odd and even numbered cylinders. This connecting rod uses a locating tab to position the connecting rod bearing.

Connecting rod bearings in later engines do not have locating tabs but are positioned by dowels in the connecting rods. The rods with dowel located bearings are marked " Even Cyl Only. . ." or " Odd Cyl Only. . .". These rods must be installed in the correct bank. They may be installed in earlier engines if the correct piston cooling jets are installed. Refer to Special Instruction (GEG02495) for complete instructions.

Crankshaft

The crankshaft transforms the combustion forces in the cylinders into usable rotating torque which powers the machine. There is a timing gear at each end of the crankshaft which drives the respective timing gears.

Interconnecting drilled passages supply pressurized lubricating oil to all bearing surfaces on the crankshaft.

Electrical System

The electrical system is a combination of three separate electric circuits: the charging circuit, the starting circuit and the lighting circuit. Each circuit is dependent on some of the same components. The battery (batteries), disconnect switch, circuit breaker, ammeter, cables and wires from the battery are common in each of the three circuits.


NOTICE

The disconnect switch must be ON to allow the electrical system to function. Some charging circuit components will be damaged if the engine is operated with the disconnect switch OFF.


The charging circuit is in operation when the diesel engine is operating. The electricity producing (charging) unit is an alternator. A regulator in the circuit senses the state of charge in the battery and regulates the charging unit output to keep the battery fully charged.

The starting circuit operates only when the disconnect switch is ON and the start switch is actuated.

The diesel engine starting circuit includes a glow plug for each diesel engine cylinder. Glow plugs are small heating elements in the precombustion chamber which promote fuel ignition when the engine is started in low temperatures.

The lighting and charging circuits are both connected on the same side of the ammeter while the starting circuit connects to the other side of the ammeter.

System Components

Starter Solenoid

A solenoid is a magnetic switch that utilizes low current to close a high current circuit. The solenoid has an electromagnet with a movable core (6). There are contacts (4) on the end of the core. The contacts are held open by a spring (5) that pushes the core away from the magnetic center of the coil. Low current will energize the coil and form a magnetic field. The magnetic field draws the core to the center of the coil and the contacts close.


SCHEMATIC OF A SOLENOID
1. Coil. 2. Switch terminal. 3. Battery terminal. 4. Contacts. 5. Spring. 6. Core. 7. Component terminal.

Starting Motor


STARTING MOTOR
1. Field. 2. Solenoid. 3. Clutch. 4. Pinion. 5. Commutator. 6. Brush assembly. 7. Armature.

Two starting motors are used to turn the engine flywheel fast enough to get the engine running.

When the heat start switch is in the Start position a low current from the switch actuates two magnetic switches (relays) which are wired in parallel. Each relay completes a higher current circuit to a solenoid on a starter motor. This current causes the solenoid to move the pinion into engagement with the ring gear on the flywheel of the engine. After the pinion is engaged the electrical contacts in the solenoid close the circuit between the battery and the starting motor. When the switch is disengaged the relay opens the circuit to the solenoid. The starting motor stops and the pinion moves away from the flywheel.

When the heat start switch is in the Heat position, a low current from the switch actuates the magnetic switch (relay). The relay completes a higher current circuit to the glow plugs. When the switch is disengaged, the relay opens the higher current circuit.

Alternator (Delco-Remy) 5S9088

This alternator is a belt driven, three phase, self-rectifying, brushless charging unit with a built in voltage regulator.

The only moving part in the alternator is the rotor (4) which is mounted on a ball bearing (6) at the drive end, and a roller bearing (3) at the rectifier end.


5S9088 ALTERNATOR
1. Regulator. 2. Fan. 3. Roller bearing. 4. Rotor. 5. Stator windings. 6. Ball bearing.

The regulator is enclosed in a sealed compartment. It senses the charge condition of the battery, the electrical system power demands and controls the alternator output accordingly.

Shut-off Solenoid


RACK SHUTOFF SOLENOID

The shutoff solenoid, when energized moves to over ride the governor action, which in turn moves the governor and fuel rack to the shutoff position.

Circuit Breaker

The circuit breaker is a safety switch that opens the battery circuit whenever the current in the electrical system exceeds the rating of the circuit breaker.

A heat sensitive metal disc (4) with a contact point (3) completes the electric circuit through the circuit breaker. Excessive high current in the electric system promotes heat in the metal disc. Heat distorts the disc, causing the contacts to open. An open circuit breaker can be reset after it is allowed to cool. Push the reset button (1) to close the contacts.


SCHEMATIC OF A CIRCUIT BREAKER
1. Reset button. 2. Disc in open position. 3. Contacts. 4. Disc. 5. Battery circuit terminals.

Wiring Schematic For 776 And 777

Reference: Make reference to SCHEMATIC FOR 776 TRACTOR AND 777 TRUCK ELECTRICAL SYSTEM, Form No. SENR7221.

Wiring Schematic For 992 And D348


ELECTRICAL DIAGRAM (THE ARRANGEMENT OF THE ATTACHMENTS MAY BE DIFFERENT THAN SHOWN IN THIS DIAGRAM)
1. Warning instrument. 2. Glow plug. 3. Glow plug relay. 4. Key switch. 5. Heat-start switch. 6. Wire to starter. 7. Water temperature contactor switch. 8. Fuel pressure switch. 9. Oil pressure switch. 10. Shut-off switch. 11. Shut-off solenoid. 12. Ammeter. 13. Ammeter shunt. 14. Battery. 15. Alternator with regulator inside.

Caterpillar Information System:

D399, G399, D398, G398, D379, G379 ENGINES Flexible Coupling<BR> (5L3395)
D399, G399, D398, G398, D379, G379 ENGINES Enclosed Clutches
D399, G399, D398, G398, D379, G379 ENGINES Hydraulic Starting System
D399, G399, D398, G398, D379, G379 ENGINES Air Starting Motors<BR> (3H3170, 3H3171)
D399, G399, D398, G398, D379, G379 ENGINES Prelubrication Pump And Air Motor
D399, G399, D398, G398, D379, G379 ENGINES Air Valves For Air Starting System
D399, G399, D398, G398, D379, G379 ENGINES Contactor Switches (Oil Pressure)<BR> 2N6955, 3N531 and 297124
D399, G399, D398, G398, D379, G379 ENGINES Contactor Switches (Oil Pressure)<BR> 9F7837 and 8L4537
D399, G399, D398, G398, D379, G379 ENGINES Shut-Off Solenoids
D399, G399, D398, G398, D379, G379 ENGINES Shut-Off Valve (Air Inlet)<BR> (2N9924, 7L5536)
D399, G399, D398, G398, D379, G379 ENGINES Shut-Off Valve (Water Temperature)<BR> (4L7108)
D399, G399, D398, G398, D379, G379 ENGINES Overspeed Contactor Switch
5.4" BORE, V12 VEHICULAR ENGINE Testing and Adjusting
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Systems Operation
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Testing And Adjusting
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Woodward PSG Governors
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Overspeed Contactor Switch
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Starter Magnetic Switch<BR> 7M4291 24V (Delco-Remy Number 1119866)
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Shutoff Solenoids
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Magnetic Switch<BR> 9F3099 24V (Delco-Remy Number 0001481)
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Oil Pressure Contactor Switches<BR> 9F7837 and 8L4537 Contactor Switch (Earlier); 9F7837; 8L4537
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Oil Pressure Contactor Switches<BR> 2N6955, 3N531 and 2N7124 Contactor Switch (Micro Switch Type); 2N6955 and 3N531; 2N7124
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Hydraulic Starting System
4.75" BORE INDUSTRIAL & MARINE ENGINE ATTACHMENTS Air Starting Motor<BR> (7L8425, 8L5052, 6L4532)
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