0347108 JOHNSON CLAMP 13.8mm

Fuel System
FUEL SYSTEM SCHEMATIC
1. Fuel priming pump. 2. Pressure relief valve. 3. Fuel return line to fuel tank. 4. Bleed valve for the fuel injection pump. 5. Fuel injection pump bleed passage. 6. Check valve. 7. Check valve. 8. Bleed valve for the fuel filter housing. 9. Fuel supply line to priming pump. 10. Fuel supply line. 11. Fuel transfer pump. 12. Check valve. 13. Fuel filter housing. 14. Fuel injection pump housing.Fuel from the fuel tank goes through fuel line (10) to fuel transfer pump (11). From the fuel transfer pump, fuel goes directly to filter housing (13), through the filter elements and into the fuel manifold in injection pump housing (14). Pressure relief valve (2) is in the fuel system to control fuel pressure. When fuel pressure gets too high, pressure relief valve (2) will open and allow some fuel to return to the fuel tank. Pump housing (14) has a separate fuel injection pump for each cylinder of the engine.Air bleed valve (4) is used to remove air from fuel pump housing (14). Use air bleed valve (8) to remove air from the fuel filter housing.Fuel priming pump (1) is used to prime the fuel system. When the fuel priming pump is operated, fuel goes from fuel supply line (10) through inlet and outlet check valves (6 and 7), then to fuel filter (13) and fuel pump housing (14). Check valve (12) is in the system to stop fuel from going back to the priming pump inlet when the priming pump is being operated.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.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 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.Fuel Injection Pump
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 spary 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.Hydra-Mechanical Governor
The governor controls engine speed by balancing governor spring force with governor weight centrifugal force. The compressed governor spring force is applied to increase the supply of fuel to the engine, while the centrifugal force of the engine driven governor weights is applied to decrease fuel to the engine.Oil pump gear (15), driven by shaft (19), provides immediate pressure oil for the servo portion of the governor. A sump in governor drive housing (16) provides an immediate oil supply for governor operation. A bypass valve in the governor drive housing maintains correct oil pressure.When