No start - fuel pump
Cargo Master
Joined: Apr 2022
Posts: 3,201
Likes: 1,704
First thing I would do personally do is actually verify power and ground at the pump when it's not working. Then go from there so your not going to a rabbit hole that could be something simple. That will tell you if it's a wiring problem or a pump/pickup problem.
Lead Driver
Joined: Oct 2005
Posts: 6,129
Likes: 1,919
From: Ponca City, OK
If you have some experience with automotive wiring an option is to run a new separate fuel pump circuit. You'd need/want a continuous duty relay probably 30 amps or bigger. It would need to be triggered from the ignition switch and you may want an additional kill switch for times you have the ignition on for the radio or whatever but don't need the fuel pump running. Then you'd need to run a hot from the relay to the pump at least 12 awg or bigger. You can just ground the pump to the frame to complete the circuit. This would tell you whether the problem is with any of the pre-existing wiring or it's at the pump/s. It would also allow you to run the truck worry free while chasing down the cause, or if you don't mind the soft code it can be permanent. It does bypass the inertia switch so something to keep in mind.
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Trailering
Joined: Apr 2024
Posts: 21
Likes: 1
Just had someone turn the key whine I check voltage at the pump, pump ran and tested 12 vilts, cycled key and it did not run and measuring 0, cycled key a few more times and it starts running again at 12 volts. Something with my wiring is what I’m gonna lean to at this point. But weird how it’s intermittent
Cargo Master
Joined: Apr 2022
Posts: 3,201
Likes: 1,704
You said the aux tank has its on fuel pump and you can switch between them? Is that just a small pump that transfers fuel to the factory tank or is there actually 2 stock style fuel pumps and the power changes between them? It's honestly just a guessing game until somebody knows exactly how the system is that is on the truck and how it works.
Cargo Master
Joined: Apr 2022
Posts: 3,201
Likes: 1,704
Ok so then it definitely sounds like a electrical issue on the truck side since the pump is losing power. I posted diagrams so you can get it to where there is no power at the pump and then trace it back and try to find out where it's losing power at along the way.