Circuit/System Description: Notes

Fuel is drawn by the fuel injection pump from the tank to the engine through the fuel supply lines. Fuel flows to the fuel filter/heater element housing, which combines a water separator, a prime pump, fuel heater element and a filter element. A mechanical fuel injection pump at the front of the engine valley includes the fuel supply pump and the high-pressure pump. The small section of the fuel pump assembly is the supply pump, which creates a vacuum to pull fuel from the fuel tank to the high-pressure pump. The vacuum varies with engine load and speed as indicated by the table below. The pump is engine-driven by the camshaft gear. From the high-pressure pump, the pressurized fuel flows to the left fuel rail. A balance pipe from the center of the left rail then feeds the right fuel rail. Each fuel rail supplies one bank of 4 fuel injectors. The fuel rail pressure sensor is mounted in the end of the right fuel rail. Fuel is used to cool and lubricate the fuel injectors and fuel injection pump. The fuel return system is designed to return this fuel to the fuel tank. If the high side fuel pressure becomes excessive, the fuel rail pressure relief valve releases the fuel into the fuel return system. The return fuel travels through the fuel cooler and then to the fuel tank.