Low Pressure Fuel Pump

The ECM activates the fuel pump for a few second after the ignition switch is turned ON to improve engine start ability. If the ECM receives an engine speed signal from the crankshaft position sensor (POS) and exhaust camshaft position sensor (PHASE), it knows that the engine is rotating, and causes the pump to operate. If the engine speed signal is not received when the ignition switch is ON, the engine stalls. The ECM stops pump operation and prevents battery discharging, thereby improving safety. The ECM does not directly drive the fuel pump. It sends the control signal to the fuel pump control module, which in turn controls the fuel pump.

Courtesy of NISSAN NORTH AMERICA, INC.