fuel priming mystery

[RangerUnicorn]

Hi all, new here, new to the Rangers. And i have a problem. Bought 1993 4.0 2wd splash (i believe). First couple of weeks everything went fine. But then the car started to refuse to fire up sometimes. It slowly got worse and worse. So i started to observe. Thats all i can do, cause i am no mechanic, know almost nothing about cars. I noticed that when i turn the key on, fuel pump comes alive, then comes off. In this situation, car fires up on a first crank. But sometimes (now more often than before), the fuel pump wont stop priming after 2 secs. With the key on, it can run forever. And if I crank, it wont fire up. But then, there is this mystery. The car parks outside. In the morning (20+ degrees celsius), if i turn the key on, pump primes forever. If its a hot afternoon (25+ or so), pump primes approx 40 seconds, then shuts off. If I crank, fires right up, runs fine. After I kill the engine and turn the key back on, pump primes 2 secs, then goes off, like it should. Crank means fireup. Then I wait like half an hour, again. Priming takes 40 secs but at least i am able to fire it up. Later in the evening, when the air temperature drops a bit, again, neverending priming with the key on, meaning no fire up. I didnt do any tests, cause i am not able to. I just replaced fuel pressure regulator and nothing changed. I believe i have enough fuel pressure. I can hear the fuel returning back to the fuel tank, so i assume fuel pump is OK & able to create enough pressure. I also took out the computer (oh my god) and a friend of mine replaced the three blue capacitors. No change. I know i should diagnose it or let it someone fix, but i am just crazy obsessed to solve it by myself. The priming mystery is killin me. And the temperature dependance. Anyone can help? And sorry for my english. Did my best.

Some more info:
the fuel is fresh
once i get it running, it runs fine i guess (didnt have a chance to compare with other 4.0 rangers, actually never seen another one around here)
i already tried to move every single cable out there, while it primes, no effect
tried to disconnect MAF, the idle regulator thing, and other stuff whle priming - no effect
fuel pump relay seems fine, cause once it works, it works also shuffled all the relays (they seem the same type, or?) and no change

Yeah, and thank you in advance!

 

[franklin2]

What about the fuel pump relay? Take it out and see what it looks like? There may be another relay in the box that is the same that you could swap it around and see if it changes anything or the problem moves.

 

[RangerUnicorn]

Yeah, i ve already tried that. I tried all the relays in the box. No change.

 

[Sleepy_z06]

Yeah, i ve already tried that. I tried all the relays in the box. No change.

Did you ever figure it out? Currently dealing with the same issue.

 

[lil_Blue_Ford]

Wonder if the fuel pressure regulator might be bad and not letting it build prime.

Ground or computer issue would be my next guess.