Ok, I see. If that were the case then it would catch - on the priming fuel - but not continue running, right? I don't get that. And it never stops while running & no codes.
Registry 8x Series V8 Swaps (20 Viewers)
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NeverFinis
SILVER Star
Yes, I believe it would catch, stumble and die in that scenario.
If it isn't a sensor issue, I would go over the harness and its connections to the fuse block/relays.
tmxmotorsports
SILVER Star
It's not blowing the fuel pump fuse?
Nope.
tmxmotorsports
SILVER Star
Ok then there has to be a loose connection. Check all ground points also check the pin going to the ecm at the ecm that triggers the fuel pump then wiggle all the wiring around and recheck. A short to ground would blow the fuel pump fuse. Also check the wiring right at the fuel pump there is also factory wiring that comes out of the cab through the floor that goes over to the fuel pump there is a connection/ connector if you look under the vehicle right at the driver rear door check to see if that is good too. A quality relay will last a very long time .
Tommy
tmxmotorsports
SILVER Star
Also pull the fuel pump fuse out and take a really good look at it fuses now days can be cheap crap check the connection holding the fuse could be loose or corroded.
I think it has to be on the signal or ground sides of the relay, because when it fails the relay doesn't activate.
Certainly can't be the fuse since it's working now and I haven't changed the fuse.
You could read continuity through the relay but it might not be able to carry enough current to run the fuel pump. You could also have a bad relay base. I have come across both of these on many occasions.
Those fuse boxes are pretty low quality. Remove them and check the underside.
The problem is that the relay isn't closing. When the relay closes, it works fine.
I did have it out. Looks ok, contacts and the crimp connections to the wires seem solid as far as I could see. Poked and pried at em with a probe.
As far as I can tell the signal side is one wire straight to the big ECM connector. I couldn't trace the ground side. I haven't pulled the ECM connector off yet.
I did use a small screwdriver to pry the sides of the relay socket contacts in a bit so they're tighter. Felt tight plugging in and removing relays, but figured it couldn't hurt.
I guess the part that bugs me about the loose connection theory is that it's never happened while driving. Thousands of miles, days at a stretch off road and it's never skipped a beat. It's only happened on starting in a parking lot. Two times about 8 months apart.
It takes more current to start than to run constant. If it's a bad connection it can't get enough current to start the motor or in this case the fuel pump. But it could be another issue with one of the other wires going to the ECM
