Fuel needle jumps

[Phil750]

On my 86 C-20 the Fuel Needle is never steady. Is there any easy fix to this problem.
Thanks for any ideas.

[tucsonjwt]

In my experience, aftermarket fuel sending unit will cause the fuel gauge to move on acceleration, stops, and turns because of the design/low quality of the sender and resistor. If your gas gauge stops moving and shows the correct fuel level at some point, then I would suspect the sending unit.

[craig@ridetech.com]

I ran into an issue on my 76 where the needle was randomly jumping. Turned out the wire from the sending unit to the gauge was pinched and my guess is that is was getting signal intermittently causing the needle to jump. After I found that I cut and respliced the wire and it's been great ever since.

[Phil750]

Thanks for your help. I will check both.

[78 Chevyrado]

Is it constantly the same amount unsteady no matter the level in the tank? If so it's probably a wiring problem of some sort.

Otherwise it should be rock steady at full, get worse towards the middle and fluctuate quite a bit on the last 1/4 of the tank. If it does this, it's the fuel sloshing, IIRC they didnt put baffles in the tanks until EFI.

It could also be a combination of both.

[78 Big10 454]

Had that problem and traced it to the wire from the sending unit as it ran along the frame on the passenger side, right below the door. It was a frayed wire that was grounding to the frame. A little electrical tape and problem solved!

[Chris' 86]

Originally Posted by 78 Chevyrado

Is it constantly the same amount unsteady no matter the level in the tank? If so it's probably a wiring problem of some sort.

Otherwise it should be rock steady at full, get worse towards the middle and fluctuate quite a bit on the last 1/4 of the tank. If it does this, it's the fuel sloshing, IIRC they didnt put baffles in the tanks until EFI.

It could also be a combination of both.

The first time that my tank got below half, this scared the hell out of me. I just bought the truck and I thought it was dumping fuel. Thought I was gonna be stranded a few miles from the house.