I have a 99 Pontiac sunfire the fuel gage floats between full and empty I know that it's not reading right. The sending unit in the take is good I tested it. So what could be causing this and how would I fix it.

Here are some suggestions:

TROUBLESHOOTING PROBLEM: The fuel gauge does not work at all...no needle movement. With the ignition switch on, remove the wire from the fuel tank sending unit and ground it to the unit housing. This removes the resistance supplied by the sending unit, and should cause the gauge to swing over to the 'Full' position. Does this happen?
Yes
No
The gauge and wiring are good. The problem is most likely with the sending unit. The sending unit must be removed for further testing. (1) Ground the sending unit wiring to a good chassis ground (instead of the sending unit housing) and watch the gauge. Does it now peg out to the 'Full' side? Yes
No
The problem is with the sending unit ground. Either the unit itself is bad or the float/arm is binding/missing. The sending unit must be removed for further testing. The power supply to the gauge has been interrupted, (check fuses), the gauge is defective, or the wire from the gauge to the sending unit is open or has a break in it. Testing the Sending Unit After the sending unit has been removed from the tank, check to make sure the float is present, intact and still floats and that there is no binding with the float arm. Reconnect the gauge wiring to the unit and ground the unit. Move the float arm up and down. If the gauge reads full in the full up position and empty in the full down position, then the sending unit is good. Verify by hooking up an ohmmeter to it and making sure it reads 8-12 ohms full and 70-73 ohms empty. If not, the sending unit needs repaired or replaced. You can easily disassemble the head of the sending unit to clean and/or repair.

It is more likely to be at the fuel tank end of the system as the fuel level float is the consantly moving part and likely to become worn and give erratic readings. Replacing the sending unit should fix the problem. Also check for a loose connection in the wiring loom near the sending unit.

The Fuel SENDING UNIT HAS FAILED And IS CAUSING This Fluxuation Of the GAGE, The Sending Unit Is Located IN the FUEL TANK & Requires TANK REMOVAL to Replace it,
NOTE;;;; IF YOU HAVE HAD THE FUEL PUMP REPLACED RECENTLY, THEN 99% PROBABILITY THAT THE INSTALLER WAS NOT VERY GENTEL WITH IT, THIS IS A COMMON REASON FOR THIS TYPE OF FAILURE.

You have a bad fuel level sensor.The fuel tank needs to come out and the sensor replaced.You don`t have to replace the pump assembly.You can get the level sensor separate.I`m not sure if the parts stores have it but I know the dealerships do.Hope this helps.Good luck.

or sending unit is worn or faulty

Yes there is a float that is connected to the sending unit in the gas tank. In order to get to it, you have to remove the tank (drain it first) and it all comes out the top of the tank. You will probably want to buy a whole sending unit to put in there. I'm not sure about yours, but the fuel pump and the sending unit may be all one piece. It's not a fun job, so you don't want to do it twice. I would change the fuel pump while i had it out anyway. Good luck!

A bad electric connector is possible. A bad tank sending unit can cause the same symptom. Usually the sending unit is a reostat mounted inside the tank.. it changes resistance depending on the float position, the resistance change causes a different voltage to the gauge or signal processor. The reostat may be a resistive plastic strip, as the float moves a contact pointer wipes the length of strip thus the change in resistance and voltage. Clear as mud?

hello, it sounds like it has something to do with your fuel sending unit located inside your gas tank,on the sending unit it has a float arm that reads the fuel level, some times that float arm gets jammed and wont show your actual fuel level,to fix this with your gas tank at least half full use a rubber mallet or any other object that wont damage the tank and with your key in the start position with the car not running but reading your gages hit the gas tank not to hard but hard enough to lodge the float arm loose, if this is unsuccessful then it will probably be a bad fuel sender location sensor located on the actual fuel sender if that's the case you'll need a new fuel sender. good luck and please send me a update or any questions let me know.

sounds like you got a malfunctioning float on your fuel pump (works like a toilet bowl) try adding magellans mystery oil (you can find it at most part houses like napa ect) to you fuel for a few tanks to see if it can loosen things up if not probably going to need to replace the part

sending unit or float in gas tank, check if any broken wires or well plugged in and then check the float for the gas.