I replaced fuel pump in car connected the new pigtail ran new grounds for the new pump and sender. Car started and ran fine all day with multiple stops and restarting. Next morning pump wouldn't cycle on pcm ignition fuse was blown replaced it . tested battery it was bad so I replaced it. Started up ran fine cycled on and off a few times. This morning it won't cycle on again all fuses and relays seem to be in working order. I'm stumped.

 

Could a bad or failing oil pressure switch cause the pump to not come on?

 

Not aware that oil pressure would have any connection with fuel pump electrical. Any fuel pump is in series with the ground or negative circuit- completing the circuit. Unless things have evolved beyond what I'm aware of. So circuit would run through fuel "gauge" circuit say and then ground out through pump. No positive direct wiring.

Reason being you don't want anything with positive 12V potential sitting in a tank of fuel. Senders for gauges were designed same idea placed in gas tanks.

You may have a connector not fully seated due to terminal dislodged or pushed out, broken locking tab maybe? Possibly nothing wrong with old pump, you must be touching base on trouble area as pump works for awhile and looses power? Look for something right in front of you, out of the norm or untouched areas. May of had a mouse even chew through wiring somewheres, intermittent connection. Check under back seat?