Lou,
I'll try to help, Going off memory here so bare with me.
First thing to check is your fuel inj. Fuse, is it OK?
The connector that goes into the fuel tank sending unit contains three wires. Black is ground. A tan wire with a white tracer is the power wire going directly to the fuel pump do you have power at this location? Remember unless your car is running you are only going to have power for two seconds after the key is turned to the run position. This is because the ECM only allows the pump to run for two seconds when the ignition is turned to the run position. The third wire is a power wire also; it is the one that is connected to the rheostat in your tank, it tells your gauge what fuel level to read depending on how much voltage it is receiving.
You have a fuel pump test lead wire on your Buick, you can supply power to this wire and the fuel pump will run if it is not bad. This wire is located behind the A.C. compressor next to the valve cover right above the header (I think it is a grey wire). Next to it will be the Tachometer test lead. (Sometimes people plug these two leads together accidentally and their tachometers go bonkers). By supplying 12 volts to this lead the pump should run, if it dont the pump may be bad.
If it does then continue on.
Next check fuel pump relay wires. The fuel pump relay is the middle relay on the passenger side fender. One of the wires connected to this relay is a dark green wire with a white tracer, located in pin A1 of the fuel pump relay wire harness socket assembly. When you turn the key to the run position the ECM triggers 12 volts for two seconds to the Dark green wire with a white tracer. In order to check this wire for power you will need some help. Get your test light on this lead and have your assistant turn the key to the run position, it should turn on the test light for two seconds, does it?
If the test light indicates you have power for two seconds then the internal Ecm relay is working. If it does not light then there is a problem with this circuit.
If it lights then turn the ignition key to off and probe the tan with white tracer wire plugged into the fuel pump relay (socket B).
Did it light up for two seconds?
If it did not light up check the black with white tracer, is it making a good ground?
If the ground is good and the tan with white tracer is not powering up you probably have a bad relay.
Also remember the oil pressure switch CANNOT cause your pump not to run (unless the pump relay is bad). It's there as a back up for the relay, and hooked in parallel. If the relay goes bad, the oil pressure switch bypasses it as long as you have 4lbs of oil pressure the fuel pump will stay running.
Hope this makes sense.
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