When you say "redid the wiring" is that from the fuel relay back or just
at the pump? On my '89 p'up the wires actually corroded in the insulating jacket of the wire. Dependending on which way I twisted the wire it would make or break the circuit.

It reads like you have current bleeding across wires in the harness. Check the connecting blocks where the interior harness meets the receptor for the engine compartment harness at the fire wall. You might have corrosion that's crossing circuits and bleeding enough voltage to make the pump relay drop out. I had the same sort of problem with my headlights. Unplugged the connecting block and gave both sides a good shot of electrical contact cleaner and I haven't had a problem since.