'77 K10 Fuel Gauge Not Accurate

[Dead_North]

Hey Gang,

My fuel gauge in my '77 Cheyenne K10 will not read past the 3/4 mark of the gauge. When I fill it appears to go to F but as I drive it doesn't want to seem to move all too much. This is for both tanks.

What do you guys think?

• Sending Unit
• Gauge itself
• Bad Ground

I apologize ahead of time, I did try to search for this issue but haven't found anything where the gauge was inaccurate the way this one is.

 

[dsteelejr]

I see your post is over a month old. Any luck with it?

My grandpa installed an aftermarket aux fuel tank on my '80 K25 and had a regular, garden variety toggle switch for the gauge and used a separate manual switch over valve to actually switch which tank you were drawing fuel from. Just a few weeks ago I had a similar problem to what you described. I took the toggle switch out and checked it with a continuity tester and found one side of the switch always had continuity, regardless of the position of the switch. It was old and wore out. I put a new toggle switch in and problem solved. I suppose even a factory switch could go bad. Might be worth checking your switch. Nothing lasts forever.

 

[Ellie Niner]

I'm not wanting to research or write a bunch if OP doesn't come back to read it, but there is a resistor on the back of the fuel gauge on many GM vehicles of this era that can cause erroneously low readings if it fails, and it's not particularly hard to replace.