Trail EXT - Problem with Fuel Level Indication

[ibelta]

Hello,
In one of the summer days, I parked my truck with minimal level of fuel.
Later that day I drove to fill the tank with gas.
I found out that the fuel meter is behavior strange as it indicates much less fuel than there is (i tapped the gas tank again while the gauge indicated 3/4 of tank).
I am not sure what is the problem but turning the ignition to on and off again will sometimes give a different readout.
Is the float may be bad? is there anything else there that can be bad (i think that it is somehow related to the extreme heat with minimal fuel I had).
How to fix it?

[maxwedge]

Usually the tank unit causes this.

[ibelta]

Is it an easy fix? how can I reach the unit and replace it?

[maxwedge]

Tank must come out not an easy job.

[B33p3r]

My 06 is doing the same thing. I received some good info from another forum and figured I'd post it here to help.
Problem: Fill your fuel tank and the gauge will go to the empty position and stay there. After a while of driving or even the next time you drive, the gauge will work its way back to reading correctly. It wll sometimes start to work then drop back to empty etc etc.
Fix: The varistor which is part of the fuel level sensor gets coated with sulfer and prevents the varistor from giving an accurate reading. You can try a fuel treatment to correct this. "Chevron Techron fuel system cleaner". I'm told this targets sulfur. after using it twice if your problem has not gone away, the fuel level sensor will have to be replaced.
I'm told most garages and dealers will want to replace the entire sending unit but it is not necessary. The fuel level sensor alone can be found on ebay. Part: ACDelco SK1159 $30.00. The tank must be dropped and pump removed as this is part of the pump unit. Once pump is removed the sensor is easy to replace. A couple hour job dropping the tank and re-installing but definately do-able as a DIY.
At the very least get the sensor only and have a garage change it for you.