Engine Operation 26 UENR0623-02 High Pressure Fuel System Illustration 19 g02493876 Typical example (1) Fuel injection pump (2) Suction control valve for the fuel injection pump (3) Pressure relief valve (4) Fuel manifold (rail) (5) Electronic unit injector (6) Fuel pressure sensor (7) Fuel transfer pump The fuel injection pump (1) feeds fuel to the high- pressure fuel manifold (rail) (4). The fuel is at a pressure of up to 160 MPa (23200 psi). A pressure sensor (6) in the high-pressure fuel manifold (rail) (4) monitors the fuel pressure in the high-pressure fuel manifold (rail).
The ECM controls a suction control valve (2) in the fuel injection pump in order to maintain the actual pressure in the high-pressure fuel manifold at the desired level. The high-pressure fuel is continuously available at each injector (5). The ECM determines the correct time for activation of the correct electronic unit injector (5) which allows fuel to be injected into the cylinder. The leakoff fuel from each injector passes through an external pipe above the electronic unit injectors. The leakoff fuel then flows to a connector block on the left-hand side of the engine. A pipe is connected from the connector block in order to return the leakoff fuel to the fuel tank.
Components of the Fuel Injection System The fuel injection system has the following mechanical components: Primary filter/water separator Fuel transfer pump Secondary fuel filter Fuel injection pump Fuel injectors Fuel manifold Pressure relief valve