G 3500 1 Ton Van V8-454 7.4L (1989)
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Oil Pressure Switch (For Fuel Pump): Description and Operation
As a back-up system to the fuel pump relay, the fuel pump can also be turned ON by the oil pressure switch. The oil pressure switch is a normally open
switch which closes when oil pressure reaches about 28.0 kPa (4.0 psi). If the fuel pump relay fails, the oil pressure switch will power the fuel pump.