Can somebody tell me what could be the different causes that would make the fuel gauge read full all the time even with a couple of gallons of gas in the take? I want to try everything before I have to drop the tank and look at the sending unit. I have an 87 z28 5.0 Camaro. Thanks.

 

Now I have => no proof <= but maybe you can investigate this:

I believe I read somewhere that if the fuel gauge is not connected to the variable resistor inside the fuel tank that follows the 'fuel float' movement then the fuel gauge will read always read 'full'. So maybe there is a 'bias' that holds the fuel gauge 'full' unless affected by the variable resistor inside the fuel tank.

I guess one thing you could try is to unhook the fuel gauge wire (but not the fuel pump wire or ground wire) going to the fuel tank and see if the fuel gauge still reads 'full'. At that point you will at least know what the fuel gage reads with absolutely no contact with the variable resistor in the fuel tank.

 

When full the fuel gauge sender (variable resistor should be 90 ohms, when empty 0 ohms. Disconnecting the wire to the sending unit will cause it to read infinite resistance causing the gauge to read full. Which maybe the problem to begin with, but most likely the sending unit is bad.

A new one from Chevy is > $600.00 and requires removal of the gas tank, which requires removal or lowering of the rearend.

 

If you jumper wire the signal wire to ground the gauge should go to empty, if it does, the sensor in the tank is bad.