1990 Buick Skylark No start

With the fuel injector connector plugged in, key on, If you probe wires, both wires should be hot?

Could be problem with ignition module?

Because your obd1, you can check codes, yourself. You use a jumper wire between the A & B terminals at your data link connector. Turn key just till the dash lites come on, no further. Then the mil on the dash starts flashing, you count the flashes to get the codes. Your looking for two digit codes.

The picture is just to show location of terminals A & B. The data link connector should be a long lower edge of dash between steering column and driver door.

When you first turn on the key, no crank, can you hear the fuel pump run for a couple of seconds? If not, I'd check voltage and ground at the fuel pump connector, engine cranking. If good voltage and ground at the fuel pump and no fuel pump action, I suspect the fuel pump.

If I remember correctly, there is an oil pressure switch in parallel with fuel pump relay on this vehicle, once you crank it enough to bring up oil pressure, the pump should run, regardless of the computer. The only thing is, I can't hear the pump run, with engine cranking. I have to use a gage and check fuel pressure.

I'll post the wiring for fuel pump.

Fuel pump wiring.

Do you have an injector pulse, engine cranking? If the computer doesn't pulse the ground, could be issue with wiring circuit--computer or ignition module.

The oil pressure switch and fuel pump relay are a redundant power supply to the pump. They are parallel circuits, one doesn't effect the other, although both may get voltage from the source.

Did you check fuel pump injector fuse for voltage? The green wire with white tracer at the relay, should be hot, initial prime or engine cranking, that voltage comes from the pcm.

Like I said, if the oil pressure switch has voltage and is functional, the pump will run, even without the relay. I don't know what else to tell you? I can't see much from here.

Good job. Glad you got it going your way.