Test Description

Test Number 1)  Turns "ON" the fuel pump if circuit 120 wiring is OK. If the pump runs, it may be a fuel pump relay circuit problem, which the following steps will locate.

Test Number 2)  The next two steps check for power and ground circuits to the relay.

Test Number 3)  Determines if ECM can control the relay.

Test Number 4)  The oil pressure switch serves as a backup for the fuel pump relay to help prevent a "no start" situation. If the fuel pump relay was found to be inoperative, the oil pressure switch circuit should also be tested to determine why it did not operate the fuel pump.

Fig 1: Chart A-5 Schematic, Fuel Pump Ckt Diagnosis (S, T & M Series)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Flow Chart A-5, Fuel Pump Ckt Diagnosis (S, T & M Series)

Courtesy of GENERAL MOTORS CORP.