In a real pickle with fuel pump issues. Advice appreciated!!

[Fless]

Thats very odd. Using a 2002 schematic there is no oil pressure switch in series with the fuel pump or the fuel pump relay. I havent seen a GM vehicle use that configuration for around 30yrs.

I'd agree. The oil pressure switch can be disconnected but the truck will run.

 

[rockola1971]

I'd agree. The oil pressure switch can be disconnected but the truck will run.

At one point back in the early 90's IIRC GM had used a oil pressure switch in series with the fuel pump relay coil (IIRC) so if there was not enough oil pressure it would prevent the engine from running by cutting the fuel off. Now the oil pressure unit at the back of the block is actually a oil pressure sensor, not a switch. It reads actual PSI pressure and thats it. It does not have any kind of switch on/off ability nor is rated for any meaningful current.

 

[exp500]

When you spliced in the new connector harness for fuel pump, are you sure the wireing is correct? Most color codes do not match pins on aftermarket connectors.

 

[rockola1971]

When you spliced in the new connector harness for fuel pump, are you sure the wireing is correct? Most color codes do not match pins on aftermarket connectors.

Good point. When you wire up a DC motor (fuel pump) backwards it causes the DC motor to run backwards and the impeller of the pump has fins that face a certain direction to create the pumping action. Just like a water pump works with its impeller. If wired backwards the fuel pump would not create any meaningful pressure.

 

[iamdub]

When you spliced in the new connector harness for fuel pump, are you sure the wireing is correct? Most color codes do not match pins on aftermarket connectors.

You might be on to something!