For some reason on my 72 chevelle the fuel gauge sometimes reads way over the full line and stays thier..Then sometimes it reads normal.Does this mean thiers a break in the wire some where?

It's grounding out some place or something wrong with the sending unit.

The sending unit is essentially a variable resistor. If some junk got into the housing, it could cause funky readings but is a remote possibility. More likely a loose ground or gauge could be going bad.
If the sending unit was grounding out (short) the gauge would see less resistance, ala low gauge level.
If the sending unit was disconnected or had an intermittant open (infinite resistance) the gauge would see high resistance, ala high gauge level.

Check the ground point behind the axle on the trunk pan and the point where the sending unit lead passes through the frame crossmember and into the trunk behind the bumper. disconnect the connections and make sure they're clean and free of rust. Get some dielectric grease and give them a light coating before reconnecting. This will inhibit the rust and corrosion and not impede the electrical connection.

Thanks for your help!

I had this problem too. Turned out the ground on the locking ring was dirty. Cleaned it and it worked good for a while, now it reads past full until I get down to 1/4 tank, then it reads fine. I think it had to do with the resistance. I will check it again soon. If I ever get time. lol

I had this problem too. Turned out the ground on the locking ring was dirty. Cleaned it and it worked good for a while, now it reads past full until I get down to 1/4 tank, then it reads fine. I think it had to do with the resistance. I will check it again soon. If I ever get time. lol


I think me and you might have the same problem haha..my gauge was working fine up until it got down to a quater tank recently..Let me know if u find out whats causing it..i will be looking into this to.

I think me and you might have the same problem haha..my gauge was working fine up until it got down to a quater tank recently..Let me know if u find out whats causing it..i will be looking into this to.

FYI, if the car sat for a lengthy bit of time (fuel degrading and crystallizing) with a full, or near full tank there could be deposits on the resistor either causing the float to stick, or bridging the resistor for a higher than normal reading.

You can check the resistance with an ohmmeter from body ground to the tan fuel sender lead behind the rear bumper, without removing the tank.

FYI, if the car sat for a lengthy bit of time (fuel degrading and crystallizing) with a full, or near full tank there could be deposits on the resistor either causing the float to stick, or bridging the resistor for a higher than normal reading.

You can check the resistance with an ohmmeter from body ground to the tan fuel sender lead behind the rear bumper, without removing the tank.


Well, last time I pulled the sending unit and moved the float up and down the gauge worked fine. That is how I know it was the ground. I think that may be the problem again. I will check soon and get back here.