Mike
I just went through all the testing procedures on a 54 chevy fuel gauge with no luck and the tank sending unit worked just like you said yours did 0 to 30 calling Classic parts was not much help they did say the stem sticks out farther on the new gauges so watch for it rubbing on the back of the bezel.
To me the needle felt as if it were a bit sticky so with two nonworking new gauges i did something i would not normally do.
Thinking this just has a disk that spins and nothing to lose I gave it a 360 spin. Thats all it took it was no longer sticky so I hooked it back up and it now moves from 0 to full with no problems
Hoda thunk it.
I however had two new guages and nothing to lose at this point. Your mileage may very...
Ken


1951/54
Basketcase