UPDATE: Still need help.
Went through a lot trying to figure this out and I have this posted on another forum, maybe someone here can give me a hand.
Here is a full picture of the problem and what we've tried that hasn't worked.
The original problem is that the car would run for awhile until it reached operating temperature, maybe a little longer. At that point it would die.
There would be no electricity in the car. dash wouldn't work at all. jumping battery does nothing. No lights come on.
The battery is in great shape, brand new and the voltage is where it is supposed to be.
When you turn the key on and off without trying to start it, the fuel pump would not come on.
Once you let it cool off, then when you turn it on, the fuel pump would come on and you could start the car.
In short you can drive it only for a few minutes at a time.
We posted on forums to get some info and we tried several things, we checked the obvious stuff first like wires and grounds.
Then we checked the air flow sensor, It seems to check out in continuity nothing sticking.
We checked for a parasitic draw. Didn't find anything.
Everything we kept checking seemed ok.
We would run the car til it died, then check the individual pieces.
We ended unchanging the starter and the alternator because they are original very old. Those work and check out fine.
We tested the wiring harness with no issues I thought.
*Did some continuity tests according to the FLM for the wiring harness oddly it doesn't match exactly so I can't honestly tell which ones to check. For instance the FLM shows a plug at 20 but there isn't one in the harness in place 20.* Everything I checked did have continuity*
We then ended up pulling those two fuel relays out and testing them and they didn't show any results following the guides that we had and then posted the info original and we were told it was bad.
That's where we were told to buy the new relays. Then we got caught up on the wiring.
I'm just not convinced that the relays are really bad. I actually took them apart to look at them honestly because I was trying to understand the wiring. I don't know anything about it, I'm a visual person so I usually can reverse engineer things.
*I replaced the relays and in doing so one of the fusible links burned out because the 5pin I bought was not a 2 solenoid relay. I got another one.* (they are not plugged in when I do the test with direct wiring for the pump) Tried both ways.
The other thing we did was check the fuel pump. We ran the car til it died, then put direct hot and ground wires to it to make sure it would turn back on, and it did.
I bypassed the fuel relays, directly ran the fuel pump from the battery to a switch so I can manually turn it on and off, wanted to make sure that the pump wasn't bad though continuity came up fine. After the car dies I can flip the switch and the fuel pump comes on, but no power to the dash.*
I forgot to mention that we did also change the ignition switch.
I also put on a clear fuel filter so I can see the gas is going through.
Any info you give is great. The car is a daily driver however, it's my sons. He is using my truck while his car is at my house. Since I work from home I don't need the truck daily, however off work, I can't use it either because it's at his house.
So now we are back to square one.
I would love this to start running for my son so I can get my truck back.
Thanks for any info you can provide.