I've replaced the fuel pump and sending unit in my 87 xj. The gauge hasn't worked since I purchased it... Well that got some thing to work... but when the tank was empty the gauge red at about 1/4" below E and when full it read about 3/8 of a tank.

Did some forum searches...

I figured I would swap gauges and I've done that figuring out I had to swap the polarity to get it to work right (swapped the wires on pins 13 & 15 on the wiring harness) but even now full reads at about 1/4 tank when full...

Did some more forum searches...

I pulled the fuel pump assembly and it reads at about 78ohms when full and 3 ohms when empty so that appears to be in the right range...

Did even more forum searches...

I was trying to map out the pin out to double check I re-wired it correctly and realized that when I start the jeep the gauge shoots up to about 3/4 tank which is about accurate right now but then when I release the ignition, it goes back down to just under 1/4 tank...

Any ideas why the start position would be different than the run position for the fuel gauge?

Cant find quite this problem anywhere...

Thanks!