Fuel Gauge

[JimT]

I am in the final stages of restoring my 1966 GMC 1000 and was hoping someone could help be trouble shoot why my gas gauge is not working. I replaced the gas tank and sending unit but the gauge only reads 1/4 full after putting 15 gallons in a 17 gallon tank... thanks in advance for any suggestions!

JimT

[GMCv6inND]

Well, we’re you able to raise and lower the float arm while it was hooked up and outside of the tank - just to watch the gage move? Does the gage move at all?
I would look at the float again now, in case it has a hole in it - I bought a new one for my sons pickup and it quit reading correctly too. Pulled it out and the brass float was crap - small holes all over it so had to buy another float.
Just something to check.

[FetchMeAPepsi]

I just rejiggered my gas gauge and tank. The gauge works off resistance. So as the gauge moves, it provides less and less resistance. Like GMCV6inND said, you need to pull it out (stick a rag in the opening for the fumes) and run the arm up and down while all the wires are connected. See if it registers.

If it stops at 1/4 tank then clean off the grounding screw on the back wall. Better? No?
See if the little wires are broken on the sending unit where the arm runs up and down. Mine was on my first one.
You have to pop the little cover off to see them. It only takes a pair of pliers.

It's a simple system so troubleshooting is just a matter of good connections. Let us know what you find!

[JimT]

Thank you guys, will get at it tomorrow!

[James]

For troubleshooting you might like to check out what I had suggested to FetchMeAPepsi.

https://6066gmcclub.com/showpost.php?p=70770&postcount=604