Oil Pressure Sensor Swtich 90 Chevy Lumina

[werknman]

At the risk of sounding ignorant, I have a few questions:
1. Where is the oil pressure sensor switch on a 1990 Chevrolet Lumina Sedan, 3.1?

2. And would this have anything to do with the Fuel Pump working or not?

Here is what happend: Car ran out of gas, and once filled with gas, wouldn't stay started. We could hear the fuel pump running, but no pressure at the throttle body. Towed the car home, changed the fuel filter and the oil at the same time (it was low on oil too, dumb kid!)....went to start, which it did, but fuel leak at fuel filter, replaced o-ring, fuel pump did work before replacing o-ring., because the car started and there was pressure at the throttle body. BUT, after replacing the o-ring, no fuel pump. Fuel Relay good, fuse good, tried jumping the fuel pump at the connector in the engine compartment, NOTHING. Frustrated, started retracing steps, which included checking oil....well, bonehead son only put in 2 qts, topped off oil.....this got me to thinking so I looked at the wiring diagram in the haynes manual, and it shows an oil pressure sensor/fuel pump switch.....thought maybe it's related to my problem, but I don't know if I am barking up the wrong tree!!! Help