my 42 ford gas gauge does exactly the same thing as yours. New gauge and new sending unit. Just like you when I remove it from the fuel tank I can get great movement on the gauge. when I put it back in no bueno. I have actually installed a ground wire that follows the wire to the gauge and attaches to the gauge. Still no bueno. I am trying to install one of the closed cell plastic floats to see of its due to a saturated float. Until then I have a stick that doesn't ever lie and works every time.
Keep them corners square and No giving up.
Robert
Commented on M38A1 F-Head Engine Rebuild, Part 2, ShopTime™ S6, Episode 39
30 Oct 11:59
That's always the conundrum. Fix it or replace it. It's only money until ya aint got no money