Fuel Pump: Description and Operation

The fuel pump is an electric pump that is controlled by the engine control module (ECM)/powertrain control module (PCM) through the circuit opening relay. When the ECM/PCM commands the fuel pump to operate, the fuel pump motor turns an impeller in the pump assembly. This causes fuel within the fuel tank to be drawn into the fuel pump inlet port. Fuel is pumped out to the fuel rail and fuel injections under pressure through the fuel feed pipe and hose. The fuel pressure is retained when the fuel pump is not running by means of a pressure control valve located within the pump. Excess fuel is returned to the fuel tank by means of a fuel return pipe.