Gas gage show full all the time

Floater in tank is stuck or switch is bad. Must open gas tank to get to the pump where floater is placed to check it.

remove the back seat and you should find two covers with wire on them, one is the fuel pump and the other is the floater, its probably stuck due to condensation. pull it out and if its rusty just wipe off the rust or sand it down with a fine grit sandpaper and ensure the floater goes up and down with ease, reinstall half way and check your gauge before putting eveything back and if that don't work you need a new one.

The floater may be stuck in the gas tank. Use a fuel cleaner in the next few fill ups and that should break it loose. If not then the float will need to be replaced.

when the tank is full the resistance is low so the power through the gage make is read full
as the tank empties , the resistance increases so the less current means the gauge reads less until empty there is little or no power , the gauge reads empty
simple check , turn the ignition off, no power , no gauge reading

Sometimes those gages go bad, or it could be the float on your sending unit is bad, that is in the gas tank, I have an older model truck that can be on empty and I can put like 10 dollars in it and it will show like it has a full tank, and we know with gas prices these days that isn't much gas lol, but more than likely it's sounds like to me that your gauge is faulty.

If you understand resistance in ohms, and you have an ohm meter you can test out the fuel gauge system. The gas gauge is essentially an ohm meter, and the fuel level sending unit is a variable resistor. as the tank becomes lower and lower on fuel, a float in the tank attached to a variable resistor sends a signal to the gas gauge, and that is how the gauge keeps track of the fuel level. Normally if the gauge pegs out when you start the engine, the sending unit in the fuel tank is bad, or the wire going to the tank has a bad connection. If you remove the sending unit you can check it with an ohm meter. A good repair manual available at most major auto parts stores will walk you through the procedure.

sounds like fuel pump is good the floater may need replacing or the wire that reads the floater may be loose

HI, i would go ahead and replace the sending unit in this vehicle. sea foam is good stuff and, if it did not fix this erratic gauge, it must be a malfunctioning sendi8ng unit. a bad ground would cause the gauge to read full all the time so, i wouldn't worry about the ground being bad at this time.

This is a faulty sending unit and, i would replace it asap if possible.

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.

Is......the problem--"the gas gage reads empty when there is fuel in the tank. OR, The gage moves when the key to turned off ?

If it's the first,
You will need to test the gage and through process of elimination, determin if the Sending unit inside the fuel tank has gone Bad.

If its the second ? - Electrical gauges will move when powered down. Normal

Testing the gauge may not be easy - just depends on your ability.
It is a simple 2-wire gauge circuit, when disconnect (usually need the fuel tank) the gage reads in one direction (either full or empty)
then when shorted-the gage reads in oppisite direction.

Of course you must select the correct wires or you may short out the wrong circuits!! Most GM vehicles use a purple wire & black wire.

A quick method I have used to check the in-take part of the gauge is this.
1st. know there is gas - 1/2 tank works best.
2nd driver's door open, key in run position, engine not running.
3rd gently lift up on the door then let if come back down, gently.
just enough to cause the gas to slosh around.
4th - keep an eye on the gas gage, a bad sending unit in the take will show up as a "twitchy" needle.

Of course, if the gage never leaves empty - sloshing won't work.
I have a known good sending unit I can plug into the vehicle and simulate different levels of fuel - if the gas gage works, I know the problem is in the tank.

Let us know.

Dave