Introduction

NOTE: The specifications given for “use again” and “permissible” are intended for guidance only and Caterpillar Tractor Co. hereby expressly denies and excludes any representation, warranty or implied warranty of the reuse of any component.

Fuel System

The sleeve metering fuel system is a pressure type fuel system. The name for the fuel system is from the method used to control the amount of fuel sent to the cylinders. This fuel system has an injection pump for each cylinder of the engine. It also has a fuel transfer pump on the front of the injection pump housing. The governor is on the rear of the injection pump housing.

The drive gear for the fuel transfer pump is on the front of the camshaft for the injection pumps. The carrier for the governor weights is bolted to the rear of the camshaft for the injection pumps. The injection pump housing has a bearing at each end to support the camshaft. The camshaft for the sleeve metering fuel system is driven by the timing gears at the front of the engine.

The injection pumps, lifters and rollers, and the camshaft are all inside of the pump housing. The pump housing and the governor housing are full of fuel at transfer pump pressure (fuel system pressure).

NOTICE
Diesel fuel is the only lubrication for the moving parts in the transfer pump, injection pump housing and the governor. The injection pump housing must be full of fuel before turning the camshaft.

This fuel system has governor weights, a thrust collar and two governor springs. Rotation of the shaft for governor control, compression of the governor springs, movement of connecting linkage in the governor and injection pump housing controls the amount of fuel sent to the engine cylinders.

Fuel from fuel tank (7) is pulled by fuel transfer pump (11) through water separator (F) (if so equipped) and fuel filter (9). From fuel filter (9) the fuel goes to housing for fuel injection pumps (14). The fuel goes in housing (14) at the top and goes through inside passage (20) to fuel transfer pump (11).

SCHEMATIC OF FUEL SYSTEM
1. Fuel priming pump (closed position). 2. Fuel priming pump (open position). 3. Return line for constant bleed valve. 4. Constant bleed valve. 5. Manual bleed valve. 6. Fuel injection nozzle. 7. Fuel tank. 8. Fuel inlet line. 9. Fuel filter. 10. Fuel line to injection pump. 11. Fuel transfer pump. 12. Fuel bypass valve. 13. Camshaft. 14. Housing for fuel injection pumps. A. Check valve. B. Check valve. C. Check valve. D. Check valve. F. Water Separator.

From fuel transfer pump (11), fuel under pressure, fills the housing for the fuel injection pumps (14). Pressure of the fuel in housing (14) is controlled by bypass valve (12). Pressure of the fuel at FULL LOAD is 30 ± 5 psi (205 ± 35 kPa). If the pressure of fuel in housing (14) gets too high, bypass valve (12) will move (open) to let some of the fuel return to the inlet of fuel transfer pump (11).

Flow Of Fuel Using The Priming Pump

When the handle of priming pump (2) is pulled out, negative air pressure in priming pump (2) opens check valve (A) and pulls fuel from fuel tank (7). Pushing the handle in closes check valve (A) and opens check valve (B). This pushes air and/or fuel into housing (14) through the fuel passages and check valve (C). More operation of priming pump (2) will pull fuel from fuel tank (7) until the fuel lines, fuel filter (9) and housing (14) are full of fuel. Do this until the flow of fuel from manual bleed valve (5) is free of air bubbles.

Constant Bleed Valve

Constant bleed valve (4) lets approximately 9 gallons of fuel per hour go back to fuel tank (7). This fuel goes back to fuel tank (7) through return line for constant bleed valve (3). This flow of fuel removes air from housing (14) and also helps to cool the fuel injection pump. Check valve (D) makes a restriction in this flow of fuel until the pressure in housing (14) is at 8 ± 3 psi (55 ± 20 kPa).

CONSTANT BLEED VALVE
4. Constant bleed valve. D. Check valve.

Operation Of Fuel Injection Pumps

The main components of a fuel injection pump in the sleeve metering fuel system are check valves (A & B), barrel (C), plunger (D), and sleeve (F). Plunger (D) moves up and down inside barrel (C) and sleeve (F). Barrel (C) is stationary while sleeve (F) is moved up and down on plunger (D) to make a change in the amount of fuel for injection.

When the engine is running, fuel under pressure from the fuel transfer pump goes in the center of plunger (D) through fuel inlet (E) during the down stroke of plunger (D). Fuel can not go through fuel outlet (G) at this time because it is stopped by sleeve (F), (see position 1).

Fuel injection starts (see position 2) when plunger (D) is lifted up in barrel (C) enough to close fuel inlet (E). There is an increase in fuel pressure above plunger (D), when the plunger is lifted by camshaft (4). The fuel above plunger (D) is injected into the engine cylinder.

FUEL INJECTION SEQUENCE
1, 2, 3. Injection stroke (positions) of a fuel injection pump. 4. Injection pump camshaft. A. Check valve. B. Check valve. C. Barrel. D. Plunger. E. Fuel inlet. F. Sleeve. G. Fuel outlet. H. Lifter.

Injection will stop (see position 3) when fuel outlet (G) is lifted above the top edge of sleeve (F) by camshaft (4). This movement lets the fuel that is above, and in, plunger (D) go through fuel outlet (G) and return to the fuel injection pump housing.

When sleeve (F) is raised on plunger (D), fuel outlet (G) is covered for a longer time, causing more fuel to be injected in the engine cylinders. If sleeve (F) is low on plunger (D) fuel outlet (G) is covered for a shorter time, causing less fuel to be injected.

Check valve (B) will not let a constant flow of fuel go through the injection pump and into the cylinder if the injection nozzle tip breaks. Check valve (B) will open when the injection pump pressure gets to 100 psi (690 kPa).

Check valve (A) will not let fuel from the fuel line go back into the injection pump when the pump plunger moves down. Check valve (A) will open when the pressure in the fuel line is 1000 psi (6900 kPa) more than the pressure in the injection pump.

Operation Of 9N3979 and 1W5829 Fuel Injection Nozzle

The fuel inlet (5) and nozzle tip (14) are part of the nozzle body. Valve (7) is held in position by spring force. The force of spring (11) is controlled by pressure adjustment screw (3). Locknut (10) holds pressure adjustment screw (3) in position. The lift of valve (7) is controlled by lift adjustment screw (2). Locknut (9) holds lift adjustment screw (2) in position. Compression seal (6) goes on the nozzle body.

9N3979 FUEL INJECTION NOZZLE
1. Cap. 2. Lift adjustment screw. 3. Pressure adjustment screw. 4. O-ring. 5. Fuel inlet. 6. Compression seal. 7. Valve. 8. Orifices (four). 9. Locknut (for lift adjustment screw). 10. Locknut (for pressure adjustment screw). 11. Spring. 12. Diameter. 13. Carbon dam. 14. Nozzle tip.

Compression seal (6) goes against the fitting of the fuel inlet (5) and prevents the leakage of compression from the cylinder. Carbon dam (13), at the lower end of the nozzle body, prevents the deposit of carbon in the bore in the cylinder head.

Fuel, under high pressure from the fuel injection pump goes through the hole in fuel inlet (5). The fuel then goes around valve (7), fills the inside of the nozzle body and pushes against diameter (12). When the force made by the pressure of the fuel is more than the force of spring (11), valve (7) will lift. When valve (7) lifts, fuel under high pressure will go through the four .0128 in. (0.325 mm) orifices (8) into the cylinder. When the fuel is sent to the cylinder, the force made by the pressure of the fuel in the nozzle body will become less. The force of the spring will then be more than the force of the pressure of the fuel on diameter (12). Valve (7) will move to the closed position.

Valve (7) is a close fit with the inside of nozzle tip (14). This makes a positive seal for the valve.

When the fuel is sent to the cylinder, a very small quantity of fuel will leak by diameter (12). This fuel gives lubrication to the moving parts of the fuel injection nozzle.

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 3/4full. 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.

WATER SEPARATOR
1. Vent valve. 2. Drain valve.

To drain the water separator, open drain valve (2) in the drain line and vent valve (1) at the top of the water separator. Let the water drain until it is all out of the water separator. Close both valves.

Governor

CROSS SECTION OF FUEL SYSTEM
1. Lever. 2. Governor housing. 3. Load stop pin. 4. Cover. 5. Sleeve control shafts (two). 6. Inside fuel passage. 7. Housing for fuel injection pumps. 8. Drive gear for fuel transfer pump. 9. Lever on governor shaft. 10. Piston for dashpot governor. 11. Spring for dashpot governor. 12. Governor springs. 13. Spring seat. 14. Over fueling spring. 15. Thrust collar. 16. Load stop lever. 17. Carrier and governor weights. 18. Sleeve levers. 19. Camshaft. 20. Fuel transfer pump. E. Orifice for dashpot.

Lever (1) for the governor is connected by linkage and governor springs (12) to the sleeve control shafts (5). Any movement of lever (9) will cause a change in the position of sleeve control shafts (5).

When lever (1) is moved to give more fuel to the engine, lever (9) will put governor springs (12) in compression and move thrust collar (15) forward. As thrust collar (15) moves forward, the connecting linkage will cause sleeve control shafts (5) to turn. With this movement of the sleeve control shafts, levers (18) will lift sleeves (21) to make an increase in the amount of fuel sent to the engine cylinders.

When starting the engine, the force of over fueling spring (14) is enough to push thrust collar (15) to the full fuel position. This lets the engine have the maximum amount of fuel for injection when starting. At approximately 400 rpm, governor weights (17) make enough force to push spring (14) together. Thrust collar (15) and spring seat (13) come into contact. From this time on, the governor works to control the speed of the engine.

GOVERNOR PARTS
10. Piston for dashpot governor. 11. Spring for dashpot governor. 13. Spring seat. 14. Over fueling spring. 15. Thrust collar.

When governor springs (12) are put in compression, the spring seat at the front of the governor springs will make contact with load stop lever (16). Rotation of the load stop lever moves load stop pin (3) up until the load stop pin comes in contact with the stop bar or stop screw. This stops the movement of thrust collar (15), the connecting levers, and sleeve control shafts (5). At this position, the maximum amount of fuel per stroke is being injected by each injection pump.

The carrier for governor weights (17) is held on the rear of camshaft (19) by bolts. When engine rpm goes up, injection pump camshaft (19) turns faster. Any change of camshaft rpm will change the rpm and position of governor weights (17). Any change of governor weight position will cause thrust collar (15) to move. As governor weights (17) turn faster, thrust collar (15) is pushed toward governor springs (12). When the force of governor springs (12) is balanced by the centrifugal force of the governor weights, sleeves (21) of the injection pumps are held at a specific position to send a specific amount of fuel to the engine cylinders.

The parts of the dashpot work together to make the rpm of the engine steady. The dashpot works as piston (10) moves in the cylinder which is filled with fuel. The movement of piston (10) in the cylinder either pulls fuel into the cylinder or pushes it out. In either direction the flow of fuel is through orifice (E). The restriction to the flow of fuel by orifice (E) gives the dashpot its function.

When the load on the engine decreases, the engine starts to run faster and governor weights (17) put force against springs (12). This added force puts more compression on springs (12) and starts to put spring (11) in compression. Spring (11) is in compression because the fuel in the cylinder behind piston (10) can only go out through orifice (E). The rate of flow through orifice (E) controls how fast piston (10) moves. As the fuel is pushed out of the cylinder by piston (10), the compression of spring (11) becomes gradually less. When springs (12) and spring (11) are both in compression, their forces work together against the force of weights (17). This gives the effect of having a governor spring with a high spring rate. A governor spring with a high spring rate keeps the engine speed from having oscillations during load changes.

When the load on the engine increases, the engine starts to run slower. Governor weights (17) puts less force against spring (12). Spring (12) starts to push seat (13) to give more fuel to the engine. Seat (13) is connected to piston (10) by spring (11). When seat (13) starts to move, the action puts spring (11) in tension. As piston (10) starts to move, a vacuum is made inside the cylinder. The vacuum will pull fuel into the cylinder through orifice (E). The rate of fuel flow through orifice (E) again controls how fast piston (10) moves. During this condition, spring (11) is pulling against springs (12). This makes the movement of seat (13) and springs (12) more gradual. This again gives the effect of a governor spring with a high spring rate.

FUEL SYSTEM COMPONENTS
5. Sleeve control shafts. 7. Housing for fuel injection pumps. 18. Sleeve levers. 21. Sleeves.

When the governor control lever is turned toward the FUEL-OFF position with the engine running, there is a reduction of force on governor springs (12). The movement of the linkage in the governor will cause fuel control shafts (5) to move sleeves (21) down, and less fuel will be injected in the engine cylinders.

To stop the engine, turn the ignition switch to the “OFF” position. This will cause the shut-off solenoid to move linkage in the fuel pump housing. Movement of the linkage will cause sleeve levers (18) to move sleeves (21) down, and no fuel is sent to the engine cylinders. With no fuel going to the engine cylinders, the engine will stop.

Air-Fuel Ratio Control With Hydraulic Override

The air-fuel ratio control limits the amount of fuel to the cylinders during an increase of engine speed (acceleration) to reduce exhaust smoke. The hydraulic override allows a maximum amount of fuel to the cylinders to start the engine.

Bolt (12) in the air-fuel ratio control limits travel of the fuel control shaft in the FUEL ON direction only. As the engine accelerates, the fuel control shaft makes contact with bolt (12) and will not go to the full fuel position. When the turbocharger gives enough air pressure to give good combustion in the cylinders, the inlet manifold pressure goes through a line to air inlet (8) into air chamber (10). The air pressure in air chamber (10) pushes on diaphram (11) which moves bolt (12) down. When bolt (12) moves down, the fuel control shaft can move to the full fuel position.

AIR-FUEL RATIO CONTROL
1. Solenoid. 2. Wire. 3. Orifice. 4. Fitting (oil outlet). 5. Screen. 6. Oil chamber. 7. Diaphram. 8. Air inlet. 9. Plunger. 10. Air chamber. 11. Diaphram. 12. Bolt.

Wire (2) from solenoid (1) is connected to the start terminal of the starter switch. When the solenoid is activated by the starter switch, oil from the rear of the right cylinder head goes through solenoid (1) to oil chamber (6). Oil pressure in oil chamber (6) pushes on diaphram (7) and plunger (9) which moves bolt (12) down. The fuel control shaft can now go to the full fuel position for easier starting.

When the engine starts and the starter switch is released, solenoid (1) closes and stops oil flow to oil chamber (6). Oil in oil chamber (6) goes through screen (5), orifice (3), and fitting (4). Oil now goes through a tube and drains into the left cylinder head. With no oil pressure in oil chamber (6), bolt (12) and plunger (9) move up. Bolt (12) will now limit the movement of the fuel control shaft until inlet manifold air pressure moves bolt (12) down.

Fuel Temperature Compensated Torque Control Group

The fuel temperature compensated torque control group is used on some agricultural engine arrangements where the fuel temperature can get very hot. When the temperature of the fuel increases, the performance of the engine decreases. The fuel temperature compensating torque control group increases the fuel setting when the fuel temperature increases to help keep engine performance normal.

FUEL TEMPERATURE COMPENSATED TORQUE CONTROL GROUP
1. Bellows. 2. Spring. 3. Rocker arm. 4. Fuel setting screw.

The space under the cover for the torque control group is completely filled with fuel when the engine is in operation. Bellows (1) senses (feels) the temperature of the fuel. As the temperature of the fuel increases, the bellows expands (gets longer) and pushes down on the end of rocker arm (3). This will cause the opposite end of the rocker arm to move up against the force of spring (2). This will also move fuel setting screw (4) up and increase the fuel setting. The increase in the fuel setting will keep engine performance the same when the fuel temperature increases.

When the temperature of the fuel decreases to the normal fuel temperature, the bellows contracts (gets shorter) and spring (2) pushes down on rocker arm (3) and fuel setting screw (4). The fuel setting will return to the normal fuel setting.

Automatic Timing Advance Unit

The automatic timing advance unit (2) is installed on the front of the camshaft (3) for the engine. The automatic timing advance unit (2) drives the gear (1) on the camshaft for the fuel injection pump. This gear is the drive for the camshaft for the fuel injection pump.

The weights (4) in the timing advance are driven by two slides (6) that fit into notches made on an angle in the weights. The slides (6) are driven by two dowels which are in the drive gear for the engine camshaft. As centrifugal force (rotation) moves weights (4) outward against the force of springs (5), the movement of the notches in weights (4) will cause the slides to make a change in the angle between the timing advance gear and the two drive dowels in the drive gear for the engine camshaft. Since the timing advance unit drives the gear (1) on the camshaft for the fuel injection pump, the fuel injection timing is also changed.

AUTOMATIC TIMING ADVANCE UNIT
1. Gear on camshaft for fuel injection pump. 2. Automatic timing advance unit. 3. Camshaft for the engine.

The automatic timing advance unit will change the timing 5 degrees. This change starts at approximately low idle rpm and is operating up through the rated speed of the engine. No adjustment can be made to the automatic timing advance unit.

Lubrication oil for the timing advance unit comes from drilled holes that connect with the front bearing for the engine camshaft.

AUTOMATIC TIMING ADVANCE UNIT
4. Weights. 5. Springs. 6. Slides.