There are 5 machine screws holding the sending unit down, and unlike modern units, the angles between the 5 units are all exactly the same. So it is possible to get the sender turned so that the float makes contact with the side of the tank and gets stuck there. I would check that first.

Also, with my stock sending unit, the float would make contact with the floor of the tank. This means I would always run out of gas with an eighth of a tank still showing on the fuel gauge. The float should NEVER touch the bottom of the tank, so make sure you check that too.


52 GMC 3/4 ton pickup
68 Big Block Vette
68 455 Firebird