Hello Form
I have a 72 olds cutlass that I’m having a problem with again lol.
Ok here I go, first the fuel gauge was pegged past full did the entire test including grounding the sending unit wire and gauge would read empty etc.
So I replace the sending unit with a new on and put 10 gallons of gas in tank, gauge was reading about half, which looked normal so I figured I’m good to go.
Over the last 2 or 3 weeks I’ve been working on the car in the garage tuning, fixing A/C etc and just last night the car would start and could not figure out why since the gauge was reading ¼ off tank fuel. I had another gauge, so I swapped gauge thinking maybe the old gauge was inaccurate, same reading ¼ of tank.
Also looked at see thought gas filter under hood and just what I suspected it’s not full and no full in tank.
What could cause a new sending unit to give gauge the wrong reading?
Its grounded new ground to body etc.
Any help would greatly appreciated, thanks in advanced.
Kevin

 

If the gauge is good, and the same as for a 1966, it will read full if you take the "hot" wire off the sending unit and leave it dangling. If you ground the wire, it will read empty. Your problem sounds like a bad sender in the tank, or the float is rubbing on something and not traveling freely.

 

Thanks for your help

I grounded the wire at the trunk that connect the sending unit, the gauge did read empty.

I never thought about disconnecting the ground. If I disconnect the ground and it still reads 1/4 could this just be a bad ground or do you think it could be the sending unit? I did buy this thing from auto zone lol.

The ground on the tank now is a shelf tapping sheet metal screw going straight to the body over axle, is there a better place to ground?

Thanks