Fuel Pump Relay

When the ignition switch is turned to the ON position, ECM will turn on the electric fuel pump by energizing the fuel pump relay. The ECM will keep the relay energized if the engine is running or cranking (ECM is receiving reference pulses from the ignition module). If no reference pulses exist, ECM turns pump off within 2 seconds after key on.

As a back-up system to fuel pump relay, fuel pump is also activated by the oil pressure switch. The oil pressure switch is normally open until oil pressure reaches approximately 4 psi (.28 kg/cm² ). If fuel pump relay fails, the oil pressure switch closes when oil pressure is obtained, operating the fuel pump. An inoperative fuel pump relay may result in extended cranking times due to the time required to build up oil pressure. Oil pressure switch may be combined into a single unit with an oil pressure gauge sender or sensor.

For additional information on fuel pump activation, refer to BASIC TESTING article and to appropriate I - SYS/COMP TESTS article in this section.