Posted on 2nd Gen. Site not to much response so hear the problem on @ off good reading took out sending unit in tank plugged back up with no fuel read E. Put 5gal. in now it reads 7/8 full. Traced wires and I am pretty sure that I got back right but if I didn't would it give me back wards reading. It is 2001 2500 with Fass pump. Didn't use draw straw tube.

 

Put more fuel in it and take the tuck out for a ride. If you did it right the fuel gauge will adjust to the correct reading in 10 minutes or so.

 

Well here is update turned switch on read 1/8 of tank turned switch off then back on back to 7/8. Check ohm on gauge ok check wire from unit to plug under driver side floor ok. Got instrument panel out is there a way to check gauge and is there a resistor between gauge and plug under truck.

 

If it is the gauge were could I buy just a gauge dealer only will sell full cluster $400.

 

You could go to the bone yard for another gauge.
Did you check for codes?
The fuel level sending unit in my truck will give readings of
up-20 ohms +/- 5% tank full
down-220 ohms +/- 5% tank empty
Let us know what you find. Good luck.