Riviera V6-3.8L SC VIN 1 (1995)
Oil Pressure Switch (For Fuel Pump): Description and Operation
DESCRIPTION
When the key is first turned "ON," the PCM energizes the fuel pump relay for two seconds to build up the fuel pressure quickly. If the engine is
not started within two seconds, the PCM shuts the fuel pump "OFF" and waits until the engine is cranked. When the engine is cranked and the
RPM signal has been detected by the PCM, the PCM supplies 12 volts to the fuel pump relay to energize the electric in-tank fuel pump.
As a backup system to the fuel pump relay, the fuel pump can also be energized by the fuel pump and engine oil pressure indicator switch. The
normally open switch closes when oil pressure reaches about 28 kPa (4 psi). If the fuel pump relay fails, the fuel pump and engine oil pressure
indicator switch will close and run the fuel pump.
An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold.
