Fuel Gauge is Flaky - HELP

[malibuRick]

My Fuel Gauge will jump to FULL when I start the car and then in a few seconds will Drop to EMPTY the warning light and beep will come on. This has no regard for how much gas I have in the car. I bought the 99 Malibu with blown engine and just swapped a 3500 and is running great, but now fixing all the other minor issues (like knowing how much gas I have in the tank - hehe). Is it sending unit or have others found similar situations and other things fixed - without dropping the tank.

[Azrael]

It could also be just a bad connection somewhere. Try removing/disconnecting the gauge cluster and re-connect/install it first to see if there's a bad connection there.

[rustyballs_69]

99-04 N-bodys had shitty sending units. Mine did the samething like a year after I bought my car. Had it replaced under warrenty then it started doing it again a few years later. It only did right after I would fill up. I would shut car off and back on and it worked again. Now i just go by mileage.