I have a question about my gas gauge. This thing just moves up and down at will. What the heck is up with it? Is it a sending unit or something? Is it a giant pain to fix/replace? Thanks for the help ahead of time. As always......I know someone will know what to do! Thanks, Paul
It sounds like you may have a frayed fuel sensor wire that is rubbing itself to ground during vibrations.
Could be a bad ground on the gauge as well. I had to re-wire mine when this happened to me. Not hard, but a bit of a pain in the @ss
are you sitting still when this happens or moving down the road? Does it matter how much fuel is in the tank?
Mine reads past full, pegged, all the time. I assume that's because the ground wire on the tank is corroded and disconnected?
Mitch, You are correct. The fuel guage is no getting a ground from the fuel tank for some reason. Could be the wire between the guage and the tank or the wire from the tank (sending unit) to ground. One simple way to check the gauage in most all GM cars is to find the connection usually found in the trunk (tan with white for 1970 to 1972 Skylarks), dissconnect it, ground it to the body and see if the guage goes to empty.
Mitch28, if it's pegged full, that's because it's not connected, either at the ground, or at the sending unit, so there's max resistance. If it's got a dead short ahead of the sending unit, it'd be pegged on empty with zero resistance. At least, that's what my '71 full-sized would be doing. Uncle Pauly, my gas gauge was doing the same thing, sometimes it'd behave, sometimes it'd be going so berserk you could hardly see the needle whipping back and forth. Turned out to be a combination of a bad gauge AND a corroded sending unit resistor. On my car, the sending unit looks like a large beer can, I think on Skylarks they're a more "normal" looking unit that's more easily found/bought/replaced. The easiest/simplest things to check are the connections on the gauge, and the ground connection at the tank. Make sure these are *perfect* before doing anything else, or you'll end up going around in circles. It's a pain, but you could get an ohmmeter and checking the resistance going into the gauge while somebody fills the tank from nearly empty, it should go up (or down?) smoothly, no jumping around. If it jumps, you need to look at the sending unit. If not, look at the gauge. It's also another pain, but you might want to drop the gas tank and doublecheck the sending unit wiring connections, etc. Once you get the tank down, it's easy to take the sending unit out, move the float up & down, and check the gauge movement.
