Quote Originally Posted by dave w View Post
Most ECM's are programmed to turn on fuel pump relay for about 3 seconds, initial key on / engine off from the ignition switch. The ECM is looking for a Distributor Reference Pulse (DRP) to turn on the fuel pump relay after about 3 seconds. Typically the green wire with a white stripe at the fuel pump relay is the wire from the ECM that "turns on" the fuel pump relay.

Most OBD1 EFI system have an oil pressure switch that will turn on the fuel pump, once the engine has about 5 PSI of oil pressure.

I once did an experiment with removing the fuel pump relay to see if the engine would start and run? About 20 seconds of cranking the engine started and continued to run until the ignition switch was turned off.

If the vehicle was in my shop, I'd unplug the relay and test the green wire with white stripe to see if the computer sends 12v with ignition switch on / engine off. No 12v on fuel pump relay green wire with white stripe ignition on / engine off = no good computer.
You confirmed my understanding as to how the system function. Thank You.