Fuel Gauge Help Needed (not typical problem)

[RPIcka]

I've searched and I couldn't find a similar situation. I recently bought a '72 K10 and the fuel gauge would only read from just over 1/4 tank when full and empty when empty. I removed the wire at the sender and grounded it and the gauge went to full, from what I've read doing that should make the gauge read empty?? Could I have a bad sender? Any ideas?

[JimKshortstep4x4]

From your description, I suspect that the resistor on the back of the dash gauge is bad. I would suggest making sure the fuse is good. Disconnect the brown sending wire at the fuse panel and ground the terminal to a known ground on the truck. If the gauge still goes to full then there is a problem with the gauge, possibly the resistor on the back of the gauge.

Jim

[cst350]

I recently had a sender problem when installing aftermarket gauges. When I researched this, I found that the sender is actually a ground, but changes its resistance depending on the sender arm. When I bypassed the sender and grounded the wire from the gauge it read full. I then took out my sender, hooked it up and ran the arm up and down to see how the gauge read. It was correct. My problem turned out to be a pin hole in the float.

[GMCJOE]

Sounds to me like your sending unit isn't working properly since the gauge reads full grounding it out. Float might be sticking after a certain point. Might be some build up on the sending unit if it sat for a long time. Pull the sending unit out of the tank and see if your float is bad, why it isn't traveling any further than 1/4 of tank, or in general what the issue is.

[AirSpeed]

Sounds like your float has a leak, take it out and see if it's full of gas. You should be able to get a new float for a few bucks. Mine did the exact same thing. If it sat empty for a while the gage would work right when I filled the tank, after a day or so the float would slowly fill with gas and the gauge would go down even though the tank was full. I bet it's the float.
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[AirSpeed]

I would be willing to bet your float is leaking. When grounded your gauge should read full, I just tried it on mine and it went all the way to full. Good luck!
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[leddzepp]

Agree with the float being full of fuel. It seems to be a common problem.

[RPIcka]

thanks guys, i'll check the float

[VetteVet]

Grounding the sender wire takes the sender out of the equation. The gauge should go to empty when the sender wire is grounded. Either the resistor on the back of the gauge is bad like Jim K said or the answer I gave you when you posted this in the electrical forum yesterday is the problem.

[RPIcka]

Can I pick up a new resistor?