Fuel gauge issue

[seanstrx276]

Hello, I was wondering if someone could please help me troubleshoot the issue with my fuel gauge in my 96 c/k1500 (454ss clone with 7.4l vortec). I just bought the truck so I have no info on the last time it worked. I replaced the fuel sending unit in the gas tank and that did nothing. Here is a video I posted on youtube of the issue. When I first turn ignition on the fuel gauge starts to move but then drops. Any idea of what I should look at first? All other gauges work correctly.
Youtube video of issue

Thanks,
Sean
96 c/k1500 (454ss clone with 7.4l vortec)

 

[ralmo94]

It could be the ground path from the tank, apart from that, it is very possible the air motor of the gauge itself is bad, comin on the 96+. You could swap in another cluster to check. I remember seeing a YouTube video of a guy replacing one with a new one, but at the time I found the video, the only available air motor for our clusters was for oil pressure. If that is indeed your issue and a swapped cluster works, you could possibly swap the gauge into your original cluster. Other than that, if you wanted to get creative, you could take it all apart and figure out how to mount an aftermarket gauge in your cluster, might be tricky to make it not look butchered.
Hopefully it's just a ground

 

[seanstrx276]

When you say it could be the ground path from the tank do you mean the ground for the sending unit (aka fuel pump)?

I also see a ground for the fuel fill tube.

Or is there another ground that I'm not seeing?

 

[ralmo94]

The sending unit needs to be grounded, I remember reading a thread don't remember if it was on here or not a couple years ago about someone just adding a new ground wire to the sending unit and it fixed there's. You should be able to check if that's your issue by clipping a wire on a clean spot of the sending unit and attaching to a good ground source. You could also check for continuety from a good ground to sending unit.

Do you have a scanner that you can check if the pcm is reading the correct volume?

If it's not, you most likely have a short in the signal wire under the truck.

Sorry I didn't watch your video before full ground to the signal wire makes it read empty, resistance to ground makes it read full. With your issue I would trace the wire all the way under the truck and give visual inspection for damaged pinched or cracked wire.