Finicky Gas Guage

[Umbop]

Recently purchased a 1988 Comanche with a 1998 4.0L swap. Gas gauge wasn't working and was always sitting on E with the light on. Previous owner told me it was the fuel sending unit. Replaced the sending unit/pump and the gas gauge worked till I took it to the gas station and turned her off. Once I turned her back on the needle was back to 0 with the E light permanently on. Occasionally the needle will go up to a quarter, but the light will stay on and the needle will return to E shortly after. Any ideas? 

[HOrnbrod]

What model/year sending unit did you use for the replacement? And what is the ignition system of your rig now? Is it still Renix or is it OBD2 from the donor.

 

Sounds like you have a polarity problem..