G 2500 3/4 Ton Van V8-350 5.7L VIN K TBI (1995)
Fuel Pump Relay: Description and Operation
OPERATION
When the key is first turned "ON" without the engine running, the control module turns a fuel pump relay "ON" for two seconds. This builds up
the fuel pressure quickly. If the engine is not started within two seconds, the control module shuts the fuel pump "OFF," and waits for ignition
reference pulses. As soon as the engine is cranked, the control module turns the relay "ON" and runs the fuel pump.
When the engine is cranking or operating, the control module receives distributor ignition reference pulses which also energize the injectors.
As a backup system to the fuel pump relay, the fuel pump is also turned "ON" by an oil pressure switch. When the engine oil pressure reaches
about 28 kPa (4 psi), through cranking the oil pressure switch will close to complete the circuit to the fuel pump.
An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The oil pressure switch will turn "ON" the fuel
pump as soon as oil pressure reaches about 28 kPa (4 psi).
