3306 DIESEL TRUCK ENGINE Caterpillar


Systems Operation

Usage:



General Information


1. Governor linkage. 2. Exhaust manifold. 3. Aftercooler. 4. Turbocharger. 5. Alternator. 6. Fan. 7. Fuel injection pump. 8. Fuel filter. 9. Fuel priming pump. 10. Cover for drive gear for fuel injection pump. 11. Housing for water temperature regulator. 12. Air compressor. 13. Inlet manifold. 14. Bracket covering timing pointer for flywheel timing marks. 15. Water pump. 16. Damper. 17. Front engine support. 18. Position for power steering pump. 19. Oil filter. 20. Oil cooler. 21. Information plates.

The 3306 Truck Engine is a 4.75 in. (120.6 mm) bore, 6.00 in. (152.40 mm) stroke turbocharged engine. It is available with a watercooled aftercooler. This engine has six cylinders with a displacement of 638 cu. in. (10.5 liters). The firing order is 1, 5, 3, 6, 2, 4.

The 3306 Truck Engine uses a Sleeve Metering Fuel System with a shutoff solenoid.

The starting system is direct electric and uses a 12 volt starting motor. It can also be equipped with an optional 24 volt system.

Fuel System

Introduction

The Sleeve Metering Fuel System is a pressure type fuel system. The name for the system is from the method used to control the amount of fuel in the fuel injection charge. This system has an injection pump and an injection valve for each cylinder. The injection pumps are in the fuel injection pump housing on the right side of the engine. The injection valves are in the precombustion chambers in the cylinder head.

Fuel System Timing

An automatic timing advance unit connects the drive sleeve on the end of the camshaft to the timing gears in the front of the engine. The unit changes the timing of the fuel system according to the engine speed to give better combustion of the fuel at all levels of engine operation. The unit in the turbocharged engine changes injection timing from 12° BTC, at 1200 rpm, to 18° BTC, at 2200 rpm. The unit in the turbocharged and aftercooled engine changes injection timing from 8° 30' BTC, at 1200 rpm, to 14° 30' BTC, at 2200 rpm.

Water Separator

Some engines have a water separator. The water separator is installed between the fuel tank and the rest of the fuel system. For efficiency in the action of the water separator the fuel flow must come directly from the fuel tank and through the water separator. This is because the action of going through a pump or valves before the water separator lowers the efficiency of the water separator.

The water separator can remove 95% of the water in a fuel flow of up to 33 gph (125 liter/hr) if the concentration of the water in the fuel is 10% or less. It is important to check the water level in the water separator frequently. The maximum amount of water which the water separator can hold is 0.8 pt. (0.4 liter). At this point the water fills the glass to 3/4 full. Do not let the water separator have this much water before draining the water. After the water level is at 3/4 full, the water separator loses its efficiency and the water in the fuel can go through the separator and cause damage to the fuel injection pump.

Drain the water from the water separator every day or when the water level gets to 1/2 full. This gives the system protection from water in the fuel. If the fuel has a high concentration of water, or if the flow rate of fuel through the water separator is high, the water separator fills with water faster and must be drained more often.

To drain the water separator, open the valve in the drain line and the valve at the top of the water separator. Let the water drain until it is all out of the water separator. Close both valves.

Fuel Flow With Engine Running


SCHEMATIC OF FUEL SYSTEM
1. Constant bleed valve. 2. Disc. 3. Siphon break orifice. 4. Priming pump. 5. Fuel injection pump. 6. Fuel injection valve. 7. Bleed valve. 8. Fuel return line. 9. Fuel supply line [optional water separator (W.S.) installation is shown by dash lines]. 10. Fuel tank. 11. Fuel filter. 12. Channel. 13. Check valve. 14. Check valve. 15. Housing for the fuel injection pumps. 16. Check valve. 17. Bypass valve. 18. Transfer pump.


FUEL SYSTEM INSTALLED
4. Priming pump. 5. Fuel injection pump. 7. Bleed valve. 11. Fuel filter. 15. Housing for the fuel injection pumps. 19. Shutoff solenoid. A. Connection for fuel supply line (9).


SLEEVE METERING FUEL INJECTION PUMP
4. Priming pump. 5. Fuel injection pump. 7. Bleed valve. 19. Shutoff solenoid. 20. Position for oil pressure shutoff (attachment). 21. Fuel ratio control. 22. Brass screw terminal. 23. Position for measurement of fuel pressure in housing. 24. Filter base. 25. Timing pin in storage position. 26. Drive sleeve. 27. Governor control shaft. 28. Cover for high idle stop and low idle stop. 29. Position for using timing pin. 30. Cover for housing. 31. 2P8315 Bracket Assembly. 32. Transfer pump drain. 33. Inlet for lubricating oil for automatic timing advance unit.

When the engine is running, transfer pump (18) pulls fuel from fuel tank (10), through fuel filter (11), and into channel (12) behind cover (30). From the channel, the fuel goes through check valve (13) into the bottom of priming pump (4), through the priming pump, out check valve (14) and into passage (34) in the housing. The fuel in the passage is the supply for transfer pump (18). The output of the transfer pump goes into housing (15).


SLEEVE METERING FUEL PUMP
12. Channel. 30. Cover for housing.

The fuel in the housing is the supply for the injection pumps and the lubricant for all the moving parts in the housing. Fuel can go from the housing in three ways.


SLEEVE METERING FUEL PUMP
5. Fuel injection pump. 16. Check valve. 17. Bypass valve. 34. Passage (to transfer pump inlet). 35. Passage to check valve.

1. Fuel injection pumps (5) send some fuel to the cylinders during injection.
2. Constant bleed valve (1) lets approximately 9 gal./hr. of fuel go back to the fuel tank, through return line (8) when the pressure in the housing is 25 to 32 psi (170 to 220 kPa). This flow takes air and heat away from the housing.
3. Bypass valve (17) keeps the pressure of the fuel in the housing at a maximum of 25 to 32 psi (170 to 220 kPa) at 2200 rpm. Fuel which goes through the bypass valve mixes with the fuel flow from the tank in passage (34). From here the mixture of fuel goes through the transfer pump and back into the housing.


CONSTANT BLEED VALVE
1. Constant bleed valve (in fitting).

Fuel Flow Using The Priming Pump And Bleed Valve

When the priming pump handle is pulled out, negative air pressure in the pump makes check valve (13) open and pulls fuel from the tank. Pushing the handle in closes check valve (13) and opens check valve (14). This pushes air and/or fuel into the housing through passage (35) and check valve (16). More operation of the priming pump will pull fuel from the tank until fuel supply line (9), fuel filter (11) and housing (15) are full of fuel. At this time the fuel flow from the bleed valve (7) will have no air bubbles.

Fuel Flow After Engine Stops Running

When the engine is running, the pressure in the housing holds some air in the fuel in a mixture. When the engine stops, the air comes out of the fuel and goes to the top of the housing. The air goes out of the housing through hole (36) in the cover and into passages (37) and (38) in the filter base. The air goes under disc (2) through scratch (39) and down through passages (40), (41), (42). Then the air goes through the top of the filter housing and the remainder of the fuel stays in the housing and filter.


SIPHON BREAK HOUSING
36. Hole. 37. Passage. 41. Passage. 42. Passage.


SIPHON BREAK FUEL FILTER BASE
2. Disc. 38. Passage. 39. Scratch. 40. Passage.

When the engine starts the next time, the fuel in the housing and in the filter will be the supply for the engine until the transfer pump pulls the fuel from the tank.

Fuel Transfer Pump


FUEL TRANSFER PUMP
43. Seal. 44. Driven gear. 45. Drive gear. 46. Camshaft for the fuel injection pump. 47. Drive sleeve. 48. Lip-type seals.

Fuel transfer pump (18) is on the front end of housing (15) for the fuel injection pumps. The output of the pump is more than the engine needs for combustion. Camshaft (46) for the fuel injection pump turns drive gear (45) in the transfer pump. Two lip-type seals (48) on the camshaft keep the fuel in the transfer pump apart from the engine oil in the compartment for the timing gears. The area between the two seals is connected to transfer pump drain (50). The drain has two functions. One function is to be an outlet for fuel or lubrication oil leakage. The other function is to give a visual indication of seal or bearing failure before the failure can be a cause for any more failures.


FUEL TRANSFER PUMP BODY
49. Outlet for lubrication oil to automatic timing advance unit. 50. Transfer pump drain. 51. Inlet for lubrication oil for automatic timing advance unit.

Fuel Priming Pump

The priming pump is on the cover of the sleeve metering fuel system. The purpose of the pump is to fill the fuel system with fuel. Operation of the pump with bleed valve (7) open will remove air from the fuel injection pump housing.

Fuel Injection Pump Operation


FUEL INJECTION PUMP OPERATION
1. Reverse flow check valve. 2. Chamber. 3. Barrel. 4. Spring. 5. Fuel inlet (fill port). 6. Retainer. 7. Plunger. 8. Sleeve. 9. Fuel outlet (spill port). 10. Sleeve control lever. 11. Lifter. 12. Camshaft.

The main components of a fuel injection pump in the sleeve metering fuel system are: plunger (7), barrel (3), and sleeve (8). The plunger moves up and down inside the barrel and sleeve. The barrel is stationary while the sleeve is moved up and down around the plunger to make a change in the amount of fuel for injection.

The plunger, barrel, and sleeve are a fitted set and they must be kept together. Lifter (11) and plunger (7) are lifted through a full stroke by each revolution of the camshaft (12). The force of spring (4) on plunger (7) through retainer (6) holds the lifter against the camshaft through the full stroke cycle.


FUEL INJECTION PUMP OPERATION
2. Chamber. 3. Barrel. 5. Fuel inlet (fill port). 7. Plunger. 8. Sleeve. 9. Fuel outlet (spill port). 11. Lifter. 12. Camshaft. A. Before injection. B. Start of injection. C. End of injection.

Before Injection

Before the engine can start or run correctly, the housing and fuel injection lines must be full of fuel and the sleeve (8) must be high enough on the plunger to close the fuel outlet (9) (spill port) during part of the stroke cycle. Chamber (2) fills with fuel through the fuel inlet (5) (fill port) which is under the level of the fuel in the housing.

Injection

Injection starts after the rotation of the camshaft lifts plunger (7) far enough into barrel (3) to close fuel inlet (5). At this time, both the fuel inlet and fuel outlet are closed. As more rotation of the camshaft lifts the plunger farther into the chamber of the barrel, the fuel in the chamber is put under more and more pressure. This pressure is felt by reverse flow check valve (1) and the fuel injection valve. When the pressure is high enough to open the fuel injection valve, injection starts. Injection stops when the rotation of the camshaft has lifted the plunger far enough to open fuel outlet (9). This puts the fuel outlet above the top of sleeve (8).

When the fuel outlet opens, it lets pressure off of the fuel in the chamber. The pressure of the fuel in the line closes the reverse flow check valve (1). With no more flow of fuel, injection valve at the other end of the line closes. This makes the injection complete. The volume of fuel in the injection charge is equal to the volume of the plunger which is lifted into the barrel between the start of injection and the end of injection.

After Injection

After injection has stopped, the camshaft lifts the plunger the rest of the way to the top of the stroke. The plunger is pushed out of the chamber by spring (4). The fuel in the housing fills the space in the chamber through the fuel outlet (9) until the sleeve closes it on the down stroke. More rotation of the camshaft lets the spring push the plunger down farther which opens fuel inlet (5). Fuel fills the rest of the chamber through the fuel inlet (5). Then the stroke cycle starts again.

Sleeve Position

The position of the sleeve on the plunger controls the amount of fuel for injection. When the position of the sleeve on the plunger is low enough that it does not cover the fuel outlet during any part of the stroke, the pump can not make pressure for injection. This is the "fuel off" position for the sleeve.

If the sleeve is in a higher position on the plunger, the pump can make pressure for injection. This is the "fuel on" position. As the sleeve position is made higher, more fuel is put into the injection charge.

Adjustments To The Sleeve Metering Fuel System

Fuel Pump Calibration

For good engine performance, it is very important to make the setting of all of the injection pumps be the same. The procedure for this is called Fuel Pump Calibration. See the Testing and Adjusting section of this book.

Fuel System Setting

The maximum injection charge is controlled by the Fuel System Setting. The correct procedure and tooling lists for adjustments to the fuel system are in the Testing and Adjusting section of this book. The correct measurement for the fuel system setting is in RACK SETTING INFORMATION.

Fuel System Operation

Engine Running

When the engine is running, any movement of the governor control shaft (1) makes a change in the speed of the engine. Counterclockwise movement (A) causes an increase in engine speed until the movement is held by the high idle stop (2). Clockwise movement (B) makes a decrease in engine speed until the movement is held by the low idle stop (3). More clockwise movement (B) moves the linkage beyond the detent (4) in the control. Still more clockwise movement (B) causes the pumps to stop injection and, because no fuel goes to the cylinders, the engine stops.


FUEL SYSTEM OPERATION
1. Governor control shaft. 2. High idle stop. 3. Low idle stop. 4. Detent. A. Counterclockwise movement. B. Clockwise movement.


GOVERNOR CONTROL SHAFT
1. Governor control shaft. 5. Groove. 6. Tooth. 7. Lever. 8. Edge of lever (7). 9. Lever.

Governor control shaft (1) has a groove (5) which fits a tooth (6) in lever (7). Any movement of shaft (1) moves lever (7) in the same direction. If the shaft and lever have counterclockwise movement (A), an edge (8) of lever (7) comes into contact with lever (9).


FUEL SYSTEM OPERATION
10. Seat. 11. Washer. 12. Governor spring. 13. Seat. 14. Riser.


FUEL SYSTEM OPERATION
13. Seat. 15. Load stop. 16. Load stop pin. 17. Lever. 18. Lever.


FUEL SYSTEM OPERATION
18. Lever. 19. Hole. 20. Pin.

More counterclockwise movement (A) pushes lever (9) against seat (10), washer (11), governor spring (12), seat (13), and riser (14). The movement of seat (13) pushes against lever (17) which works like a bellcrank and pushes load stop pin (16) up. The load stop pin (16) can be pushed up until it is in contact with the load stop (15). This is the limit for the movement toward maximum fuel for injection. At the same time the lower end of lever (18) is in the groove in riser (14). As the riser moves, lever (18) works like a bellcrank and moves pin (20) which is in the top end of the lever. The outer end of pin (20) has the shape of a ball. It fits in a hole (19) in the bottom part of lever (23). The turning of lever (23) makes lever (24) turn the fuel control shaft (21) through spring (22). This makes an increase in the fuel for injection to the cylinder.


FUEL CONTROL SHAFT
19. Hole. 21. Fuel control shaft. 22. Spring. 23. Lever. 24. Lever. 25. Pin.

Starting the Engine

When starting the engine, the governor control shaft is in the middle position. The linkages in the housing work in almost the same manner as when the engine is running. The only difference is in the function of a spring (C) which is between seat (13) and riser (14). When the engine is running, the force from the weights in the governor is enough to cause compression of spring (C) until the seat (13) and riser (14) are in contact. For starting, the force of spring (C) is enough to push the riser to the full fuel position. This lets the engine have the maximum amount of fuel for injection for starting. The limit for the amount of fuel for injection is the position of the air-fuel ratio control.


FUEL SYSTEM OPERATION
10. Seat. 11. Washer. 12. Governor spring. 13. Seat. 14. Riser. C. Spring.

Before the speed of the engine is up to low idle speed, the governor weights make enough force to push spring (C) together and riser (14) and seat (13) come into contact. From this time on, the governor works to control engine speed.

Stopping the Engine Manually

Maximum clockwise movement (B) of the governor control shaft stops the engine. If the governor control shaft (1) is not at the low idle position, clockwise movement (B) lets lever (9) move back away from the governor spring (12). Less compression in governor spring (12) lets riser (14) and seat (13) move away from the weight end of the shaft. The lower end of lever (18) is in the groove in riser (14). As the riser moves, lever (18) works like a bellcrank and moves pin (20) which is in the top end of the lever. The outer end of pin (20) has the shape of a ball. It fits in a hole (19) in the bottom part of lever (23). The turning of lever (18) makes lever (23) push against lever (24) which turns the fuel control shaft (21).

This makes a decrease in the amount of fuel for injection to the cylinder.

When the governor control shaft (1) is in the low idle position, more clockwise movement (B) makes pin (27) in the end of lever (28) move against lever (26). Lever (26) works as a bellcrank. As it turns from the pressure of pin (27) the other end of the lever (26) moves against the pin (25) in lever (24). Lever (24) is tight on the fuel control shaft (21) and more movement in that direction causes the pumps to stop injection and, because no fuel goes to the cylinders, the engine stops.


FUEL SYSTEM OPERATION
1. Governor control shaft. 9. Lever. 12. Governor spring. 26. Lever. 27. Pin. 28. Lever. 29. Shaft. B. Clockwise movement.

In some applications, a contact switch on the control panel for the operator activates the electric shutoff solenoid to stop the engine.

Stopping the Engine with Solenoid Shutoff

Activate To Run Solenoid


SHUTOFF SOLENOID (Activate To Run)
30. Solenoid. 31. Spring. 32. Shaft.

The function of the shutoff solenoid is similar whether it is an "activate to run" or "activate to shutoff" type. With either shutoff solenoid, the engine can be stopped without effect from the position of the governor control. The activate to run solenoid is always connected to electrical power while the engine is running. The solenoid (30) pulls in shaft (32) putting spring (31) in compression. When the electrical power to the solenoid stops, spring (31) pushes shaft (32) against lever (34). Lever (34) has a pin (35) which comes in contact with edge (36) of lever (37) and pushes lever (37) in the direction shown.


SHUTOFF HOUSING
34. Lever. 35. Pin.


FUEL SYSTEM OPERATION
29. Shaft. 36. Edge. 37. Lever. 38. Housing.

Lever (37) is tight on shaft (29) which is through housing (38). On the other end of shaft (29), lever (26) moves in the same direction. Lever (26) pushes against pin (25) in lever (24). Lever (24) is tight on the end of the fuel control shaft (21). The turning of lever (26) makes lever (24) turn the fuel control shaft (21) in the same direction. This stops the engine by putting the sleeves low on the plungers so there is no injection. This movement is independent of governor action because a spring (22) connects lever (23) and lever (24) on the fuel control shaft (21). Lever (24) can turn the fuel control shaft to the fuel off position by bending spring (22) without changing the position of the parts of the governor first.


FUEL CONTROL SHAFT
19. Hole. 21. Fuel control shaft. 22. Spring. 23. Lever. 24. Lever. 25. Pin.

Activate To Shutoff Solenoid


SHUTOFF SOLENOID (Activate To Shutoff)
30. Solenoid. 33. Shaft.

Activate to shutoff solenoids work on the other end of lever (34). The end of shaft (33) is behind lever (34). When the electrical power is on, the solenoid pulls in on shaft (33). This moves lever (34) in the same direction as an activate to run solenoid would move the lever. The rest of the linkage moves in the same way to stop the engine.

Governor

The governor for the Sleeve Metering Fuel System is of the mechanical type. It works to keep the speed of the engine from changing when there is an increase or decrease in load when the engine is running with governor control shaft stationary.


GOVERNOR
1. Seat. 2. Washer. 3. Governor spring. 4. Seat. 5. Riser. 6. Tachometer drive shaft. 7. Race. 8. Bearing. 9. Race.

Carrier (12) for weights (10) is held on one end of the camshaft by bolts. Tachometer drive shaft (6) is through the center of the governor parts. The shaft has a radial hole through the driven end. A pin (14) is through this hole and fits into slot (13) in the carrier on both sides of the shaft.


GOVERNOR WEIGHTS
6. Tachometer drive shaft. 10. Weight. 11. Pin. 12. Carrier. 13. Slot. 14. Pin.

Weights (10) are connected to carrier (12) by pins (11). Weights (10) and pins (11) work like bellcranks and pivots. When the camshaft and carrier (12) turn, the outer parts of weights (10) move out from the center. The inner parts push against race (9), bearing (8), and race (7) (thrust bearing). The thrust bearing removes the turning movement but puts the thrust against the shoulder of riser (5). Riser (5) is against seat (4) which is against governor spring (3).


FUEL SYSTEM OPERATION
4. Seat. 15. Load stop. 16. Load stop pin. 17. Lever. 18. Lever.

Governor spring (3) and washer (2) are in compression between seat (1) and seat (4). Seat (1) is held in position by the lever on the governor control shaft. There is a balance between the forces from weights (10) and governor spring (3) as long as the load on the engine does not change.

When there is a decrease in the load on the engine the engine starts to make an increase in speed. The weights in the governor turn faster causing the outer parts of the weights to move out farther. This puts more force against the thrust bearing. The thrust bearing pushes riser (5) which puts more compression on governor spring (3). At the same time the lower end of lever (18) is in the groove in riser (5).

The movement of riser (5) moves lever (18) to make a decrease in the amount of fuel for injection. With less fuel, the engine has a decrease in speed. The governor has this action again and again until the governor is in balance. When the governor is in balance the engine speed will be the same as it was before there was a decrease in load.

If there is an increase in the load on the engine, the engine starts to make a decrease in speed. The weights in the governor turn slower. The thrust from the weights against the riser will be less, so the spring pushes the riser to the right.

The movement of riser (5) makes lever (18) move the fuel control shaft to make an increase in the amount of fuel for injection. With more fuel, the engine runs faster. The governor has this action again and again until the governor is in balance. When the governor is in balance the engine speed is the same as it was before the engine had an increase in load.

Fuel Ratio Control

The fuel ratio control will limit the amount of fuel for injection during an increase in engine speed (acceleration). The purpose is to keep the amount of smoke in the exhaust gas at a minimum.

When the engine is running, air pressure from the inlet manifold is in chamber (1) of the control. The combination of the force from the air pressure and spring (2) makes a balance with spring (3). The balance controls the position of bolt (4). When the governor control is moved to make an increase in engine speed, the linkage moves to turn the fuel control shaft to put more fuel into each injection.


FUEL RATIO CONTROL
1. Chamber. 2. Spring. 3. Spring. 4. Bolt.

Turning force is put on the fuel control shaft through a spring and lever. This lever is connected through linkage to lever (6). Lever (6) is held by bolt (4) of the fuel ratio control through pin (5).


FUEL RATIO CONTROL
4. Bolt. 5. Pin. 6. Lever.

When the adjustment of the fuel ratio control is correct there will be enough increase in the fuel for injection to make the engine accelerate rapidly. If the adjustment is correct, there will not be too much smoke in the exhaust when the engine accelerates.

Fuel Injection Valve

Fuel, under high pressure from the injection pumps, is sent through the fuel lines to the fuel injection valves. When the fuel under high pressure goes into the nozzle assembly, the check valve inside the nozzle opens and the fuel goes into the precombustion chamber. The injection valve changes the fuel to many very small drops of fuel. This gives the fuel the correct characteristics for good combustion.


CROSS SECTION OF THE PRECOMBUSTION CHAMBER AND FUEL INJECTION VALVE
1. Fuel injection line. 2. Nut. 3. Glow plug. 4. Body. 5. Nozzle assembly. 6. Precombustion chamber.

Glow Plugs

Glow plugs are an aid for cold weather starting. During cold weather starting, the pressure in the cylinders made by the compression stroke is not enough to start combustion of the fuel injection charge. Activating the glow plugs for the correct length of time heats the precombustion chambers to the temperature which is necessary for combustion when the engine is turned for starting. After combustion starts and the starting motor is no longer necessary to keep the engine running, more operation of the glow plugs heats the precombustion chambers until the engine is running smoothly.

Air Inlet And Exhaust System


AIR INLET AND EXHAUST SYSTEM (ILLUSTRATED WITH AFTERCOOLER)


1. Aftercooler housing. 2. Exhaust outlet. 3. Turbine wheel housing. 4. Air outlet. 5. Compressor wheel housing. 6. Air inlet. 7. Cylinder head. 8. Exhaust manifold. 9. Exhaust inlet. 10. Cylinder bore.

The air inlet and exhaust system components are: air cleaner, aftercooler (if so equipped), inlet manifold, cylinder head, valves and valve system components, exhaust manifold, and turbocharger.

Clean inlet air from the air filter is pulled through the air inlet (6) of the turbocharger by the turning compressor wheel. The compressor wheel causes a compression of the air. On engines with an aftercooler, the air next goes to aftercooler housing (1). The aftercooler cools the air. The air then goes to the inlet manifold which is part of cylinder head (7). When the intake valves open, the air goes into the engine cylinder and is mixed with the fuel for combustion. When the exhaust valves open, the exhaust gases go out of the engine cylinder and into exhaust manifold (8). From the exhaust manifold, the exhaust gases go through the blades of the turbine wheel. This causes the turbine wheel and compressor wheel to turn. The exhaust gases then go out exhaust outlet (2) of the turbocharger.

Turbocharger

The turbocharger is installed on the exhaust manifold. All the exhaust gases from the engine go through the turbocharger.

The exhaust gases go through the blades of the turbine wheel. This causes the turbine wheel and compressor wheel to turn which causes a compression of the inlet air.


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.

When the load on the engine goes up more fuel is put into the engine. This makes more exhaust gases and will cause the turbine and compressor wheels of the turbocharger to turn faster. As the turbocharger turns faster, it gives more inlet air and makes it possible for the engine to burn more fuel and will give the engine more power.

Maximum rpm of the turbocharger is controlled by the fuel 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 fuel system setting is higher than given in the 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 and goes through passages in the center section for lubrication of the bearings. Oil from the turbocharger goes out through the oil outlet port in the bottom of the center section and goes back to the engine lubricating system.

The fuel system 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 fuel and the high idle speed setting.

Aftercooler

The aftercooler cools the air coming out of the turbocharger before it goes into the inlet manifold. The purpose of this is to make the air going into the combustion chambers more dense. The more dense the air is, the more fuel the engine can burn efficiently. This gives the engine more power.

Timing Gears

The timing gears are at the front of the cylinder block. Their cover is the housing for the timing gears. The timing gears keep the rotation of the crankshaft, camshaft, and fuel injection pump in the correct relation to each other. The timing gears are driven by the crankshaft gear.


TIMING GEARS
1. Drive gear for fuel injection pump. 2. Idler gear for fuel injection pump. 3. Camshaft gear. 4. Crankshaft gear. 5. Idler gear for oil pump. 6. Drive gear for oil pump.

Valves And Valve Mechanism

The valves and valve mechanism control the flow of air and exhaust gases in the cylinder during engine operation.

The intake and exhaust valves are opened and closed by movement of these components; crankshaft, camshaft, valve lifters (cam followers), push rods, rocker arms, and valve springs. Rotation of the crankshaft causes rotation of the camshaft. The camshaft gear is driven by, and timed to, a gear on the front of the crankshaft. When the camshaft turns, the cams on the camshaft also turn and cause the valve lifters (cam followers) to go up and down. This movement makes the push rods move the rocker arms. The movement of the rocker arms will make the intake and exhaust valves in the cylinder head open according to the firing order (injection sequence) of the engine. A valve spring for each valve pushes the valve back to the closed position.

Valve rotators cause the valves to have rotation while the engine is running. This rotation of the valves keeps the deposit of carbon on the valves to a minimum and gives the valves longer service life.

Lubrication System

Lubrication System Components


LUBRICATION SYSTEM SCHEMATIC
1. Oil supply for variable timing mechanism. 2. Oil supply for turbocharger. 3. Oil pressure connection. 4. Camshaft bores. 5. Oil passage through rocker shaft to rocker arm. 6. Oil manifold. 7. Turbocharger. 8. Piston cooling. 9. Oil cooler bypass. 10. Oil pump. 11. Oil cooler. 12. Filter bypass. 13. Oil sump. 14. Oil filter.


LUBRICATION SYSTEM COMPONENTS (Illustrated with Aftercooler)
1. Oil supply for variable timing mechanism. 2. Oil supply for turbocharger. 15. Oil return for turbocharger.


LUBRICATION SYSTEM COMPONENTS (Illustrated with Aftercooler)
9. Oil cooler bypass. 11. Oil cooler. 12. Oil filter bypass. 14. Oil filter. 16. Oil filler. 17. Oil level gauge.

Oil Flow Through The Oil Filter And Oil Cooler

With the engine warm (normal operation), oil comes from the oil pan (6) through the suction bell (9) to the oil pump (7). The oil pump sends warm oil to the oil cooler (10) and then to the oil filter (4). From the oil filter, oil is sent to the oil manifold (1) in the cylinder block and to the oil supply line (2) for the turbocharger. Oil from the turbocharger goes back through the oil return line (3) to the oil pan.


FLOW OF OIL (ENGINE WARM)
1. Oil manifold in cylinder block. 2. Oil supply line to turbocharger. 3. Oil return line from turbocharger. 4. Oil filter. 5. Bypass valve for the oil filter. 6. Oil pan. 7. Oil pump. 8. Bypass valve for the oil cooler. 9. Suction bell. 10. Oil cooler.

With the engine cold (starting conditions), oil comes from the oil pan (6) through the suction bell (9) to the oil pump (7). When the oil is cold, an oil pressure difference in the bypass valve (installed in the oil filter housing) causes the valves to open. These bypass valves give immediate lubrication to all components when cold oil with high viscosity causes a restriction to the oil flow through the oil cooler (10) and oil filter (4). The oil pump then sends the cold oil through the bypass valve for the oil cooler (8) and through the bypass valve for the oil filter (5) to the oil manifold (1) in the cylinder block and to the supply line (2) for the turbocharger. Oil from the turbocharger goes back through the oil return line (3) to the oil pan.


FLOW OF OIL (ENGINE COLD)
1. Oil manifold in cylinder block. 2. Oil supply line to turbocharger. 3. Oil return line from turbocharger. 4. Oil filter. 5. Bypass valve for the oil filter. 6. Oil pan. 7. Oil pump. 8. Bypass valve for the oil cooler. 9. Suction bell. 10. Oil cooler.

When the oil gets warm, the pressure difference in the bypass valves decrease and the bypass valves close. Now there is a normal oil flow through the oil cooler and oil filter.

The bypass valves will also open when there is a restriction in the oil cooler or oil filter. This action does not let an oil cooler or oil filter with a restriction prevent the lubrication of the engine.

Oil Flow In The Engine

From the oil manifold in the cylinder block, oil is sent through drilled passages in the cylinder block that connect the main bearings and the camshaft bearings. Oil goes through drilled holes in the crankshaft to give lubrication to the connecting rod bearings. A small amount of oil is sent through orifices near the main bearings to make the pistons cooler.

Oil is sent through passages to the rocker arm shaft. Holes in the rocker arm shafts let the oil give lubrication to the valve system components in the cylinder head.

The oil supply passage for the rocker arms is in a different location in the engine w/spacer plate. Engines w/o a spacer plate have an oil passage from the rear of the cylinder block to a head bolt hole in the block. The oil flows around the head bolt, up through the cylinder head and rocker arm shaft bracket, to the rocker arm shaft.


ROCKER ARM OIL SUPPLY (Engines without spacer plate)

Engines w/ spacer plate have an oil passage from the rear of the cylinder block that goes below the head bolt hole and connects with a drilled passage that goes up next to the head bolt hole. A hollow dowel connects the vertical oil passage in the cylinder block to the oil passage in the head. The spacer plate has a hole with a counterbore on each side that the hollow dowel goes through. An O-ring is in each counterbore to prevent oil leakage around the hollow dowel. Oil flows through the hollow dowel into a vertical passage in the cylinder head to the rocker arm shaft bracket. The rocker arm shaft has an orifice to restrict the oil flow to the rocker arms. The rear rocker arm bracket also has an O-ring that seals against the head bolt. This seal prevents oil from going down around the head bolt and leaking past the head gasket or spacer plate gasket. The O-ring must be replaced each time the head bolt is removed from the rear rocker arm bracket.

The air compressor gets oil from the oil manifold in the cylinder block through an external line.


ROCKER ARM OIL SUPPLY (Engines w/ spacer plate)

The idler gear gets oil from a passage in the cylinder block through a passage in the shaft for the idler gear installed on the front of the cylinder block.

The automatic timing advance unit gets oil from drilled passages in the body of the fuel transfer pump. This oil comes from an external line.

The turbocharger gets oil from the oil manifold through an external line.

After the lubrication oil has done its work, it goes back to the engine oil pan.

There is a bypass valve in the oil pump. This bypass valve controls the pressure of the oil coming from the oil pump. The oil pump can put more oil into the system than is needed. When there is more oil than needed, the oil pressure goes up and the bypass valve will open. This allows the oil that is not needed to go back to the engine oil pan.

Cooling System


COOLING SYSTEM SCHEMATIC
1. Radiator top tank. 2. Shunt line. 3. Coolant outlet. 4. Regulator to aftercooler vent line. 5. Water temperature regulator. 6. Inlet line to aftercooler. 7. Aftercooler to radiator vent line. 8. Aftercooler. 9. Cylinder head. 10. Radiator. 11. Water pump. 12. Return line from aftercooler. 13. Cylinder block. 14. Cylinder liner. 15. Coolant inlet. 16. Oil cooler. 17. Bonnet.


COOLANT FLOW
3. Coolant outlet. 5. Water temperature regulator. 6. Inlet line to aftercooler. 8. Aftercooler. 9. Cylinder head. 11. Water pump. 12. Return line from aftercooler. 13. Cylinder block. 15. Coolant inlet. 16. Oil cooler. 17. Bonnet. 18. Internal bypass. 19. Air compressor. 20. Outlet hose from air compressor. 21. Inlet hose to air compressor.

All Caterpillar Truck Engines must have shunt type cooling systems. This type cooling system helps prevent pump cavitation (air bubbles caused by low pressure). It keeps a positive pressure of coolant at the inlet of the pump at all times.

Water pump (11) is on the left front side of the engine. It is gear driven by the timing gears. Coolant from the bottom of the radiator (10) goes to the water pump inlet. The rotation of the impeller in water pump (11) pushes the coolant through the system.

If the engine is equipped with an aftercooler (8), some of the coolant flow goes through inlet line (6) for the aftercooler and into aftercooler (8). As the coolant goes through aftercooler (8), it cools the inlet air for the engine. The coolant comes out of aftercooler (8) through return line (12). The coolant goes through return line (12) and into bonnet (17). In bonnet (17) the coolant flow from the aftercooler mixes with the rest of the coolant flow from water pump (11). This other flow came through engine oil cooler (16). Bonnet (17) sends the coolant into cylinder block (13).

Inside cylinder block (13) the coolant goes around cylinders (14) and up through the water directors into cylinder head (9). The water directors send the flow of coolant around the valves and passages for exhaust gases in cylinder head (9). Here the water temperature regulator (5) controls the direction of the flow. If the coolant temperature is less than normal for engine operation, water temperature regulator (5) is closed. The only way for the coolant to get out of cylinder head (9) is through the internal bypass. The coolant goes through the internal bypass into water pump (11). Water pump (11) pushes the coolant through the cooling system again. When the coolant gets to the correct temperature, water temperature regulator (5) opens and coolant flow is divided. Most of the coolant goes to the lower chamber of radiator top tank (1) and through the radiator. The remainder goes through the internal bypass to water pump (11). The amount of the two flows is controlled by water temperature regulator (5).

NOTE: Water temperature regulator (5) is an important part of the cooling system. It divides coolant flow between the radiator and the internal bypass as necessary to maintain the correct temperature. If the water temperature regulator is not installed in the system, there is no mechanical control, and most of the coolant will take the path of least resistance thru the internal bypass. This will cause the engine to overheat in hot weather. In cold weather, even the small amount of coolant that goes thru the radiator is too much, and the engine will not get to normal operating temperatures.

Radiator top tank (1) is divided into two chambers (upper and lower) by a baffle. A small air and coolant vent tube connects them. Shunt line (2) is located as low as possible in the upper chamber. As coolant comes into the lower chamber of radiator top tank (1), the coolant which has air in it flows through the vent tube to the top chamber. The air makes a separation from the coolant in the top chamber. The coolant flows down shunt line (2) to the pump inlet. The air stops in the upper chamber until there is enough pressure for it to leak out the radiator cap.

Earlier engines have vent lines inside to let the air out when the cooling system is filled. Later engines have the vent lines on the outside. The standard 3306 Truck Engine must have a vent line from the regulator housing to the top of the radiator. The 3306 Truck engine with aftercooler (8) must have vent line (4) from the regulator housing to aftercooler housing (8). It also must have vent line (7) from aftercooler housing (8) to the top of radiator (10).

Coolant For Air Compressor


COOLANT FLOW IN AIR COMPRESSOR
19. Air compressor. 20. Outlet hose. 21. Inlet hose.

The coolant for the air compressor (19) comes from the cylinder block through hose (21) and into the air compressor. The coolant goes from the air compressor through hose (20) back into the front of the cylinder head.

Cooling System Components

Water Pump

The centrifugal-type water pump has two seals, one prevents leakage of water and the other prevents leakage of lubricant.

An opening in the bottom of the pump housing allows any leakage at the water seal or the rear bearing oil seal to escape.

Fan

The fan is driven by two V-belts, from a pulley on the crankshaft. Belt tension is adjusted by moving the belt tightener.

Aftercooler

The aftercooler cools the inlet air for the engine. When the engine is running coolant flow goes through the aftercooler.

Basic Block

Cylinder Block And Liners

On later engines a steel spacer plate is used between the cylinder heads and the block to eliminate liner counterbore and to provide maximum liner flange support area (the liner flange sits directly in 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 liner and the cylinder block.

Pistons, Rings And Connecting Rods

The piston has three rings; two compression 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 into the piston. Pistons in earlier engines used compression rings with straight sides. Pistons in later engines use compression rings which are of the KEYSTONE type. KEYSTONE rings have a tapered shape and the movement of the rings in the piston groove (also of tapered shape) results in a constantly changing clearance (scrubbing action) between the ring and the groove. This action results in a reduction of carbon deposit and possible sticking of rings.

The oil ring is a standard (conventional) type and is spring loaded. Holes in the oil ring groove provide for the return of oil to the crankcase.

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

Piston cooling jets, located on the cylinder block main bearing supports, throw oil to cool and give lubrication to the piston components and cylinder walls.

Crankshaft

The crankshaft changes 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.

The bearing surfaces on the crankshaft get oil for lubrication through passages drilled in the crankshaft.

Vibration Damper

The twisting of the crankshaft, due to the regular power impacts along its length, is called twisting (torsional) vibration. The vibration damper is installed on the front end of the crankshaft. It is used for reduction of torsional vibrations and stops the vibration from building up to amounts that cause damage.


CROSS SECTION OF A TYPICAL RUBBER VIBRATION DAMPER
1. Flywheel ring. 2. Rubber ring. 3. Inner hub.

The rubber damper is made of a flywheel ring (1) connected to an inner hub (3) by a rubber ring (2). The rubber makes a flexible coupling between the flywheel ring and the inner hub.

The viscous damper is made of a weight (1) in a metal case (3). The small space (2) between the case and weight is filled with a thick fluid. The fluid permits the weight to move in the case to cause a reduction of vibrations of the crankshaft.


CROSS SECTION OF A TYPICAL VISCOUS VIBRATION DAMPER
1. Solid cast iron weight. 2. Space between weight and case. 3. Case.

Electrical System

The electrical system has three separate circuits: the charging circuit, the starting circuit and the low amperage circuit. Some of the electrical system components are in more than one circuit. The battery (batteries), circuit breaker, ammeter, cables and wires from the battery are all common in each of the circuits.


NOTICE

The disconnect switch must be in the ON position to let the electrical system operate. There will be damage to some of the charging circuit components if the engine is running with the disconnect switch in the OFF position.


The charging circuit is in operation when the engine is running. An alternator makes electricity for the charging circuit. A voltage regulator in the circuit controls the electrical output to keep the battery at full charge.

The starting circuit is in operation only when the disconnect switch is put in the ON position and the start switch is activated.

The starting circuit has a glow plug for each cylinder of the diesel engine. Glow plugs are small heating units in the precombustion chambers. Glow plugs give aid for ignition of the fuel when the engine is started in temperatures that are low.

The low amperage load circuit and the charging circuit are both connected to the same side of the ammeter. The starting circuit connects to the opposite side of the ammeter.

Charging System Components

Alternator (Prestolite) 2P1204


2P1204 ALTERNATOR

The alternator is driven by two V type belts from the fan pulley. It is a 24 volt, 19 ampere unit with a regulator which has no moving parts (solid state) installed on the side opposite the pulley. The alternator is made up of the following parts: head assembly on the drive end, rotor assembly, stator assembly, rectifier and heat removal assemblies, brush and holder assembly, head assembly on the ring end, and regulator.

Alternator (Delco-Remy) 9L5938


ALTERNATOR (DELCO-REMY)

The alternator is a three phase self-rectifying charging unit. The alternator is driven from the crankshaft pulley by V type belts.

The only part in the alternator that has movement is the rotor. The rotor is held in position by ball bearings at both ends.

Alternator Regulator (Delco-Remy)


ALTERNATOR REGULATOR
1. Plug (over the voltage adjustment screw). 2. Connector.

The alternator regulator controls the alternator output according to what the battery and the other components in the electrical system need.

The alternator regulator is a part of the alternator and it is a solid state (no moving parts) type regulator.

Starting System Components

Starting Motor

The starting motor is used to turn the engine flywheel fast enough to get the engine running.


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

The starting motor has a solenoid. When the start switch is activated, the solenoid will move the starter pinion to engage it with the ring gear on the flywheel of the engine. The starter pinion will engage with the ring gear before the electric contacts in the solenoid close the circuit between the battery and the starting motor. When the circuit between the battery and the starting motor is complete, the pinion will turn the engine flywheel. A clutch gives protection for the starting motor so that the engine can not turn the starting motor too fast. When the start switch is released, the starter pinion will move away from the ring gear.

Solenoid

A solenoid is a magnetic switch that uses low current to close a high current circuit. The solenoid has an electromagnet with a core (6) which moves. There are contacts (4) on the end of core (6). The contacts are held in the open position by spring (5) that pushes core (6) from the magnetic center of coil (1). Low current will activate coil (1) and make a magnetic field. The magnetic field pulls core (6) to the center of coil (1) 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.

Magnetic Switch

A magnetic switch (relay) is used sometimes for the starter solenoid or glow plug circuit. Its operation electrically, is the same as the solenoid. Its function is to reduce the low current load on the start switch and control low current to the starter solenoid or high current to the glow plugs.

Other Components

Circuit Breaker

The circuit breaker is a safety switch that opens the battery circuit if the current in the electrical system goes higher than the rating of the circuit breaker.

A heat activated metal disc with a contact point makes complete the electric circuit through the circuit breaker. If the current in the electrical system gets too high, it causes the metal disc to get hot. This heat causes a distortion of the metal disc which opens the contacts and breaks the circuit. A circuit breaker that is open can be reset (an adjustment to make the circuit complete again) after it becomes cool. Push the reset button to close the contacts and reset the circuit breaker.


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

Shutoff Solenoid


ACTIVATE TO SHUTOFF SOLENOID

When activated, the activate to shutoff solenoid moves the fuel control shaft to the fuel off position. The solenoid can be activated by any one of several sources. The most common is the manually operated momentary switch activated by the operator.


ACTIVATE TO RUN SOLENOID

When shut off, the activate to run shutoff solenoid moves the fuel control shaft to the fuel off position. The solenoid can be shut off by any one of several sources. The most common is the manually operated key switch activated by the operator.

Caterpillar Information System:

3306 DIESEL TRUCK ENGINE Shutoff Solenoid
3306 DIESEL TRUCK ENGINE Series Parallel Switches<BR> 9L4590 12V (Delco-Remy Number 1119845)
3306 DIESEL TRUCK ENGINE Starter Magnetic Switches<BR> 5L5886 12V (Delco-Remy Number 0001486)
3306 DIESEL TRUCK ENGINE Starter Solenoid<BR> 9S7976 24V (Prestolite Number SAT-4103)
3306 DIESEL TRUCK ENGINE Starter Solenoids
3306 DIESEL TRUCK ENGINE Starter Motors
3306 DIESEL TRUCK ENGINE Starter Motors<BR> 9L3597 12V (Delco-Remy Number 1114129), 7G9132 12V (Delco-Remy Number 1114773)
3306 DIESEL TRUCK ENGINE Alternator Regulator
3306 DIESEL TRUCK ENGINE Alternators
3306 DIESEL TRUCK ENGINE Flywheel Housing Bore
3306 DIESEL TRUCK ENGINE Flywheel Housing Runout
3306 DIESEL TRUCK ENGINE Flywheel Runout
3306 DIESEL TRUCK ENGINE Testing And Adjusting
3306 DIESEL TRUCK ENGINE Introduction To The Troubleshooting Guide
3306 DIESEL TRUCK ENGINE Primary Engine Test For Low Power
3306 DIESEL TRUCK ENGINE Low Power Troubleshooting - (Diagnosis with Chassis Dynamometer)
3306 DIESEL TRUCK ENGINE Primary Engine Test For High Fuel Consumption
3306 DIESEL TRUCK ENGINE High Fuel Consumption Troubleshooting - (Diagnosis with Chassis Dynamometer)
3306 DIESEL TRUCK ENGINE Problem With Vehicle Or Vehicle Operation
3306 DIESEL TRUCK ENGINE Misfiring And Running Rough
3306 DIESEL TRUCK ENGINE Too Much Exhaust Smoke - Black or Gray
3306 DIESEL TRUCK ENGINE Too Much Exhaust Smoke - White Smoke; Blue Smoke
3306 DIESEL TRUCK ENGINE Difficult Starting - Engine Crankshaft Turns Freely
3306 DIESEL TRUCK ENGINE Difficult Starting - Engine Crankshaft Will Not Turn; Engine Crankshaft Turns Too Slowly
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