98 Blazer
So when I turn the key to on... the fuel pump cycles normally.
Sometimes when I shut the truck off though... the pump will cycle and quit, and other times it will seem to continue to run, or slowly quit running for longer than normal.
Truck runs / drives fine, just curious if this is an issue I need to address to avoid future fuel pump problems. This is the second pump within 2 years. It is a spectre pump.
Any info on this ???

Thanks
Brandon

 

only should run on about 2 seconds and stop after ignition turned off. keep your filter changed, interval is 25k your pump will live alot longer

 

The oil pressure sending unit supplies voltage to the fuel pump when oil pressure is above approximately 7psi, (along with the fuel pump relay). When the ignition is shut off, the fuel pump relay deactivates the fuel pump after approximately 2 to 3 seconds. If the oil pressure sensor contacts stick, or residual oil pressure remains above 7 psi, the fuel pump will continue to run until the residual pressure bleeds down and/or the contacts open.

The OPSU is located near the base of the distributor. There are three wires in the OPSU connector: tan with white stripe comes from instrument cluster, grey goes to the fuel pump, and orange is hot at all times. An easy test to confirm a faulty OPSU is disconnect the electrical connector at the OPSU. Start the engine, allow it to idle for a few seconds then shut the engine off. The fuel pump should run for approximately 2 to 3 seconds and shut off. If it does, OPSU is faulty.

EDIT: Not all years and models have this redundant circuit, (1998 4.3L is equipped with it).