99 cavalier fuel gauge jumps?

It sounds like the fuel gauge sender unit is faulty, probably causing a wiring problem with other dash dials. Also sounds like you already full of fuel. The float and sender unit need checking and/or replacing.
(float in fuel tank). The fuel tank needs to be drained completely to do this work. Is it something you can do ? If not, it's not a major operation for a mechanic and the parts are cheap. Good luck... Red.

if the car is fuel injected, holding the gas pedal to the floor will actually cut off your fuel injectors - which may make it worse. You need to check fuel pressure, you want to make sure the fuel pump isn't bad. Also, check your battery.

Hope this is helpful :-)

-Scott

to check it . wire at the fuel tank gauge unplug it the black and purple wire for gauge. put a variable resistor , fuel gauge is rated 0 to 90 ohms. So variate the resistor and see if fuel gauge move. if it does fuel sender have problem or inside tank wire

Tank sending unit is bad.

Possibly a bad ground wire at the sender on the tank,

Check for that first before tearing into the dash to replace the guage.

you have a bad sending unit ,its inside the fuel tank,you have too drop the tank too replace it!!

The fuel sender unit (inside the tank) has malfunctioned i think or there is too much resistance on the wire which is caused by a rusty/corroded connection - Go to a wreckers and try a different one or just get a brand new one but it sounds like the sender unit float gets to a point then jams quite common....

The float is sticking in the fuel tank.Could be expensive if the float is part of the fuel pump.

The fuel pump as a gage sender that monitors the gage in the dash. I would replace the fuel pump .
Very common problem

Good Luck

I have the same problem on my 99 ZR2 Blazer. This is the rheostat in the gas tank. I bought my part in Ebay for $27. The only issue is that you have to drop the gas tank and pull the sending unit to install. Hope this helps, I hear from other message boards that it is a very common problem in these vehicles.