Originally Posted by mickblock
Of course it has a relay. Just get a 30 amp relay, find it's fuse box location in your manual and swap it.
And I think it's the oil pressure switch that energizes the fuel pump when the engine is running.
Well, he'd need to have a 89+ to have a power distribution box, 86-88 Rangers have inline fuse links. Fuses are mounted on passenger side inner fender, green plug is fuel pump, brown plug is ECC relay.
My 88 had ran for quite some time with the oil level sender disconnected (IIRC some 2.9 equipped models may never even have that). Still will run with pressure switch disconnected.
Really sounds like the relay is working (wait till you see how much Ford wants for one), but it can be tested on a bench; but if you're not sure how a relay works, start there and it will be strait forward on how to test it. The problem sounds like it's on the grounding control side of the relay from the PCM (either always grounded/short, or the computer is grounding it all of the time for whatever reason).
Try and pull codes with out the reader, if you're not getting any sanity out of the computer.......... Not saying that it's bad (how would I be able to tell based on the information found so far?
, not common for them to crap out (any signs of moisture exposure?), but something to keep in mind as you're trying to figure this out).
Bad grounds can also do some strange things. A few people have had this same issue, but always been hit and miss to find it - very inconsistent. Really need to look at everything involved. Wiring diagrams are absolutely helpful on these sort of issues (the vehicle specific ones).