fuel gauge pegged, 90 xj

any info will be looked at. so my problem has been since I bought the jeep, 90 xj, 4.0/aw4 , have swapped out gauge with known good one without any change, fuel gauge reads way over full no matter how full or empty the tank is, how do I go about checking this without dropping the tank, right now tank should be around 1/2 full according to miles driven since last fillup. have been refueling every 200 miles on the trip odometer and usually accepts around 19 gallons.

Renix fuel gauge calibration:

Empty has 1 ohm resistance

Half tank has 44 ohm resistance

Full tank has 88 ohm resistance

Measure the sending unit's resistance while "exercising" it through its full range of motion.

While you have the wire disconected to do the testing Joe has posted above, check the gauge to see if it reads empty. If not you have a short in the wire between gauge & sender.

will check it in the a.m. thanks for the input guys, been thinking a short or the sender itself but was lazy .

Most likely a bad ground