Did the gas gauge work 15 years ago when you installed the new sending unit? Or never did work right?
Depending on the answer to that, you might want to explore the idea that the float arm is hitting the side of tank somehow. Sounds like your float is floating. Sounds like your sending unit produces the right variation in Ohms
The sending unit screws allow very limited “clocking” options of the float. Adjustment to the sending unit might be needed to ensure no interference.
