0339620 JOHNSON SEAL, Upper

Fuel System Schematic
(1) Fuel tank. (2) Fuel return line. (3) Priming pump. (4) Fuel injection nozzle. (5) Fuel injection line. (6) Fuel injection pump. (7) Primary fuel filter. (8) Check valves. (9) Fuel transfer pump. (10) Secondary fuel filter. (11) Bleed valve. (12) Fuel injection pump housing. Fuel is pulled from fuel tank (1) and through primary fuel filter (7) by fuel transfer pump (9). Priming pump (3) is used to fill the system with fuel and remove air from the system.Primary fuel filter (7), priming pump (3) and fuel transfer pump (9) make up the fuel supply pump.Fuel transfer pump (9) and bleed valve (11) maintain a fuel pressure of approximately 135 kPa (20 psi) inside fuel injection pump housing (12). The constant flow of fuel through the bleed valve helps to maintain a more constant fuel temperature and to remove air from the fuel system.Fuel injection pumps (6), one for each cylinder of the engine, are located in the injector pump housing. The fuel injection pump receives fuel from a manifold inside the fuel injection pump housing and pushes the fuel at a very high pressure, through fuel injection lines (5) to fuel injection nozzle (4). The fuel injection nozzle (4) has small holes in the tip that change the flow of fuel to a very fine spray that gives good fuel combustion in the cylinder.Fuel that is not needed for injection flows out of the injection pump housing through bleed valve (11) and back to the fuel tank.Fuel Supply Pump
Fuel Supply Pump
(1) Fuel transfer pump. (2) Hand primer pump. (3) Fuel inlet. (4) Fuel outlet. (5) Primary fuel filter. Fuel is drawn from the fuel tank and through primary fuel filter (5) on the fuel supply pump. Primary fuel filter (5) removes foreign material from the fuel before the fuel moves to hand primer pump (2) or fuel transfer pump (1).Hand primer pump (2) is screwed into the body of the fuel supply pump. The hand primer pump is used to fill the low pressure side of the fuel system with fuel and remove air from the system. For example, the hand primer pump should be used to fill the system and remove air when the secondary filter is changed.The fuel transfer pump is a double acting piston pump and is used to supply low pressure fuel [approximately 135 kPa (20 psi] to the fuel injection pump. With each stroke of the double acting piston pump against the piston spring, fuel is delivered to the injection pump across a pressure-side check valve. At the same time fuel is sucked through the primary fuel filter and through a suction check valve.
Piston Displacement Against The Spring
(1) Fuel transfer pump. Hand primer pump. (3) Fuel inlet. (4) Fuel outlet. (5) Primary fuel filter. (6) Roller tappet. (7) Cam. (8) Rod. (9) Inlet check valve (suction side). (10) Inlet check valve (suction side). (11) Outlet check valve (pressure side). (12) Outlet check valve (pressure side). (13) Piston. (14) Spring. When the hand primer pump plunger is pulled up, fuel flows out of the primary filter and past inlet check valve (10). As the primer pump plunger is pushed down, the inlet check valve closes and the fuel is pushed past outlet check valve (12) into the low pressure side of the fuel system.Fuel transfer pump (1) is moved by cam (7) (eccentric) on the fuel injection pump camshaft. As the fuel injection camshaft turns, it pushes roller tappet (6) which pushes rod (8) into the chamber. The fuel flows past inlet check valve (9) and into the area behind the pump plunger. Spring pressure closes both inlet check valve (10) and outlet check valve (11). Outlet check valve (12) is pushed open when fuel pressure in the chamber is higher than the outlet check valve spring pressure.
Piston Displacement From The Spring
(1) Fuel transfer pump. (2) Hand primer pump. (3) Fuel inlet. (4) Fuel outlet. (5) Primary fuel filter. (6) Roller tappet. (7) Cam. (8) Rod. (9) Inlet check valve (suction side). (10) Inlet check valve (suction side). (11) Outlet check valve (pressure side). (12) Outlet check valve (pressure side). (13) Piston. (14) Spring. As the camshaft continues to turn, spring (14) pushes the plunger and roller tappet out of the plunger chamber. The fuel that was behind the plunger is pushed out of the tranfer pump through outlet check valve (11) by the pressure of spring (14). At the same time, fuel is pulled past inlet check valve (10) and into the plunger chamber. Spring pressure closes both inlet check valve (9) and outlet check valve (12). The pump is now ready to start another cycle.Fuel flow is variable. However zero fuel flow is not possible since displacement is not only spring dependent, but fixed through direct connection of piston (13) through rod (8) to cam (7). Therefore, even at high line pressures, small piston motion (fuel flow) is possible, requiring a bleed (pressure relief) valve on the discharge side of the fuel pump.Fuel Injection Pump
Fuel Injection Pump
(1) Constant bleed valve. (2) Fuel inlet. (3) Oil inlet port. The fuel injection pump sends an exact amount of fuel, at the exact time and at very high pressure to the fuel injection nozzle.Fuel flows from the secondary filter into fuel injection pump housing fuel inlet (2). The fuel flows inside the injection pump housing to the six injector pumps. Fuel not needed to fill the injector pumps flows out of the pump housing through constant bleed valve (1) and back to the fuel tank. The constant bleed valve keeps the low pressure fuel inside the injector pump housing at approximately 250 kPa (36 psi).The fuel injection pump and governor use engine oil for lubrication. Pump plunger. Lubricating oil enters the pump housing at oil inlet port (3).The oil lubricates the roller tappets and camshaft bearings. The oil flows through the camshaft roller bearing and into the governor housing. The oil drains out through the fuel injection front bearing into the