2nd Gen Non-Engine/Transmission Fuel gauge stopped working. Not the usual sender failure!

[Erska]

Hello.

I installed Airdog 150gph system on my truck and took the fuel tank module out of the tank of course. I checked the sender because I have been aware of this kind of failure.
I read the whole scale with the ohm-meter and it was fine even though I tried wave the sender sideways a little when I was doing it. No loose contact.

Anyway, now my fuel gauge reads complete zero and fuel light stays on all the time.
I have a body lift so I get my head between the tank and bed, and I took the fuel tank module electrical connector off, installed the ohm-meter once again on the two middle pins on the sender and it showes 104ohms. What I have heard the scale is 10-110ohms. 10 is full and 110ohm is empty.

So I put 20 litres of fuel in it and watched how the ohm-meter went from 104 to 84ohms. So with all reason, the actual sender is working!
Well, it's still dead. Anyway, I tried to pull the wiring harness on the truck gently between the frame and the tank and my father said that the fuel gauge went quickly on full position for a second.

So that was a short circuit for a while.

Is the problem in the wiring from the tank to the sender? I guess the fuel gauge don't need anything else from the tank to work tahn the correct resistance ,right?

Do you guys have a complete electrical wiring diagram for my 1998. 5-1999 3500 24v truck?
Any thoughts?

Thanks!

 

[DFerverda]

I would check which wire was ground, i believe it is the orange one, but i would meter it.
That said i would add a different ground to it, to see if it lost it's ground. If you wiggled the wire harness and it responded, something is going on. If you can pull the wire loom apart before it gets too big, you may find a high joint or an open or a ground /cross. I had a taillight problem and it was a corroded wire in the wire loom in the frame where it made a turn and went from inside to outside the frame.
Good luck.