fuel gauge not working

[brad242]

The fuel guage on my m1028 is not working. I was wondering what should i start with to fix it. It is not working after warming up it has plenty of fuel, it used to be stuck on 1/4 tank but i guess it finally gave up. Any ideas are greatly appreciated.

 

[Barrman]

The -20 manual has a great trouble shooting section that talks you through checking just about everything on the truck that can break.

The fuel gauge section tells you to ground the sender wire at the tank, turn on the key and see what the gauge does. Needle to E means the sender is bad or not grounded. Needle past F means the gauge is bad or you have an open circuit.

The manual takes you a few steps further. Read the manual, it was written to help people keep these trucks running.

 

[niferous]

My sending unit was bad after I tested it as per the -20. Now it works but bounces around really bad. Any ideas as to what I need to check. I did start by cleaning the spot where it ground near the tank on the frame but that didn't help.

 

[Barrman]

I would say to check the pink wire every inch of the way from the sender to the gauge. Also, the grounds for the gauge panel. There is a huge collection of ground wires bolted to the top of the parking brake pedal housing over on the side.

I write all of that because GM gauges historically are very slow to move and one moving fast just doesn't fit the profile. Mine now that it works rarely gets above 1/2 tank even when full. Then it will slowly as I drive move up to around 3/4 until the level gets below that and it follows the proper level on down to E. I need to pull the sender, just don't want to right now. I can live with a guess for the top half of the tank and close to accurate info for the bottom half.

 

[niferous]

What should I be checking for in the wire? Constant voltage?

 

[Barrman]

Mainly for breaks, broken insulation, corroded connections and anything else that might cause it not to conduct all the time.