Fuel Gauge reading full all the time

[ricnor]

As title really, it's a 1997 K2500 Suburban 4x4 auto 454. I haven't used the sub for a while but got in it the other day and it fired up all fine and I then looked to see what fuel I had left only to see the needle right over to full. Well I know it is nearly empty and I've never had the guts to fill the thing or should that be had the funds to fill it to the top, so know it is wrong.
I got under the truck and unclipped the rear most wiring connector just infront of the fuel tank but the gauge still reads full.
I suspect either the gauge is faulty (so is there anyway of checking) or the sender in the tank or wires in the tank have shorted (again anyway of testing without removing the tank).

[777stickman]

It could be the gauge or wiring or sending unit. Turn the key to run (engine off) and have some one watch the gauge while you wiggle the wiring around the top of the tank. The connectors there are known to get hot and somewhat melt. Also take a rubber mallet and hit the tank a couple of times. Good luck.

[j cAT]

with the fuel guage at max this would indicate that the ground is open or the in tank resistor is open.

this would produce max voltage 2.5volts or more to create the full indication.

the in tank sensor should read 40-250 ohms.

with low fuel level should be near 40 ohms. if open then its the sensor.

since it was setting around for a while rodents like to chew on wires.

[ricnor]

Again thanks for the quick replies, I did have to change the fuel pump a few years ago and did see that the wires had been getting hot but all had been fine till recently.
Rodents are an issue where I live but I looked all along the run I could and found no issues. I haven't had the dash out as yet incase they have got in that area but the fuel gauge is the only one not working correctly.
I think I am coming to the conclusion it is the in tank wiring or the float/sender itselfso will try wiggling the wires and a rubber mallet before dropping the tank yet again.