new float, still bad guage reading??

[69 XCamper]

I replaced the leaky float in the gas tank sending unit. Tested the operation on the unit outside the tank by grounding it, and all works fine at the guage. But, when I install the sending unit, it only reads 1/8 of a tank when it should read close to full. I've removed & installed it three times & same result. And yes, I did check the float...it does float. Any ideas? I'm baffled.

[jhow66]

Sounds like your tank is not grounded good.

[cdowns]

run a ground wire right from the sendind unit to the cab

[69 XCamper]

Just tried a new ground wire, still just reads 1/8 tank. If I disconnect the lead wire to the sending unit, the guage goes up and past full. When I put the lead back on the terminal, it goes back down to 1/8 reading on guage.

[LudwigTheMad]

have you checked the ohm reading on the sending unit....it could be bad (and yes I know it's new...)

I belive it's suposed to go from short ( o reading) to 95 ohms.


If the sending unit reads good then take the wire off the back short a temp wire to it and take a reading accoss the wires, you should get a reading of about 0.

then put a resistor across the wires where you shorted them before and read the other end again, you should read the same as if you put your meter acrross just the resistor.

if any of these readings are off the wire is prob. bad.

You could just say screw it and rerun a new wire to see if that is the problem.....might be faster than trouble shooting. (if your tank is in the cab.)

Hope I helped.

[Hutch]

I have the same issue with the fuel guage on my 71.
The float works fine out of the tank but when inside the guage is way off.
I took ithe sender out of the tank and it appeared to work fine had a full range on the guage then after putting it back in the tank it went bonkers again.
I have some ideas such as the ground as others have mentioned and installing another spare that I have.
Only trouble doing this is the seat in my truck does not tilt forward and to do it right I have to remove it.
As for now I just keep the tank full.
Post your results here if you find out what the issue is.

Have fun

[lngbed71]

Pinched wire around the door jam hardware, driver's side, is what happened to me. Though I was going crazy until I found it. My guage did what you are talking about.