Fuel Supply System
An electric fuel pump (located inside fuel tank as an integral part of the fuel gauge sending unit) supplies fuel under pressure to the throttle body assembly. A fuel pump relay controls fuel pump operation. When the ignition switch is turned on, the fuel pump relay activates the fuel pump for 1 1/2-2 seconds to prime the injector. If the ECM does not receive reference pulses (engine cranking) from the distributor after this period, the ECM deactivates the fuel pump relay. The fuel pump relay will be activated again when the ECM receives distributor reference pulses.
As a back-up system to the fuel pump relay, the fuel pump can also be turned on by the oil pressure sender. The sender has 2 circuits internally. One circuit operates the oil pressure indicator in the instrument panel. The second circuit is normally an open switch which closes when the oil pressure reaches about 4 psi (.3 kg/cm2 ). If the fuel pump relay fails, the oil pressure sender will close and run the fuel pump.