Fuel Pump: Description and Operation

Fig. 2. Cross sectional view of fuel pump:

The electric fuel pump used is of the multi-cell roller type, driven by a permanent magnet field-type electric motor, Fig. 2. The function of the pump is to supply fuel, under pressure, to the injectors. The pump capacity is greater than that needed by the engine, so pressure in the system is always maintained. Because the fuel pump is of a one-speed positive displacement design, it requires a pressure regulator device. When pressure inside the pump exceeds a predetermined limit, a pressure relief valve bypasses fuel back into the suction line. A check valve is also used to maintain fuel system pressure when the engine or fuel pump are not operational. The pump operates when the ignition switch is turned to the On position, but will stop if the engine is not started within 3 seconds. The pump operates continuously when the ignition switch is in the Start position.