Fuel Gauge Pegged Past Full

[mrmel2you]

Need some help/input fellas. Doing a full gauge swap into my '90 MJ, the gauge cluster came from an '89 XJ. No matter what I do, all gauges work except for the fuel gauge, it pegs way past the full mark (5 o'clock position). I ran a new full ground wire to the connector, tied pins 5 and 10 together, same thing. Someone mentioned that maybe the fuel gauge is wired backwards/opposite from my original gauge. Said something about he had to switch two wires to get his to read right. Not sure if he meant the wires near the tank or just switch out two pins on the connector. If it was the pins----which two pins? Picture(s) would really help too. Many many thanks in advance fellas, thank you, Papa Mel