You burned up your fuel gauge. I just ordered a new one yesterday. The previous owner converted my 54 3100 to 12v. They did everything they should have to adapt the truck to 12v except step down the voltage from 12v to 6v for the fuel gauge. They are very sensitive. I ran through a series of test to confirm it was a bad fuel gauge but the number one indicator was the volt meter showed 12v entering the gauge. The cheapest replaced I could find was on classicparts.com They even accept a promocode of "stovebolt". You have the choice of 6v or 12v replacement. They are about $10 cheaper than anyone else plus cheaper shipping. With shipping my cost was $63. This is OEM correct for your truck.

http://www.classicparts.com/Fuel-Gauges/products/850/

Last edited by dgrinnan; 06/20/2016 12:45 PM.

Dave from Northern Kentucky
My 54 3100