A while back I pulled the under bed gas tank out of my '48 Chevy 1 ton dually with military pick up bed for cleaning and sending unit replacement.
The sending unit for the gauge looked like it could be original but upon removal showed to be non-functional because rust had frozen the moving parts. The sending unit is a Delco part and has the rheostat on the top of the unit where it sits outside of the fuel in the tank. A rod runs down to a gear that moves when the float--made of cork!--moves up or down. This is very different from the universal replacement part where everything sits inside the tank and the float is made, not surprisingly, of plastic.
Upon examining the new part it was obvious that it wasn't going to work because the float arm was clocked 90* from where it should be, with no way to modify the orientation. I had purchased it before starting the job from an eBay supplier who assured me it was the proper one for my application. As it turns out the unit is too deep and even if I would have bent the shaft 90* to fit my tank, the geometry wasn't going to allow the float to move enough to give useful readings.
I'm strictly a backyard mechanic and I often find myself puzzling through a repair, often resorting to modifying new replacement parts that just don't seem to fit correctly. In this case I was out of luck and figured I'd have to find another replacement part that would work.
Not wanting to spend even more money I took another look at the old part and thought I might as well try to get it unstuck. Liberal application of Sea Foam Deep Creep and 12 hours of waiting and the darned thing freed up! I cleaned everything as well as I could and when I ohm tested it it works fine! It's going back in over the weekend and I hope to have a functional fuel gauge for the first time in years.
I love it when old parts still work!
