Fuel gauge is way off.

I have an '89 Laredo and the fuel gauge is way off. It goes from full to empty in about 70 miles of driving, but I can get about 240 miles out of 15 gallons with it. It has a brand new fuel pump and sending unit, that was again installed by the previous owner just before I got it (and yes he gave me the recipt for the parts and I crawled under it and looked and it's all shinny and new). So this leads me to think it's the gauge. Is there anything I can do to fix this other than having to swap out the entire gauge cluster?

may not be the gauge cluster, PO may have bent the float arm and that causes the gauge to read inaccurately

The cluster works off of OHMs from the tank sending unit. Its either a bad sending unit in the tank or they bent the float arm upon install.

I would try the sending unit before the cluster.

I'd try the sending unit before the cluster too. First check the ground to the pump though, on the early years the ground for the sender and the pump is shared and if the ground is starting to get crummy, the increased resistance will result in a float voltage at the ground end of the sender, which will result in a very inaccurate reading.

Does the gauge at least move the right direction? If they put a 91-95 sender in it, it will go backwards and too fast. A correct year sender usually just goes too fast or too slow compared to the level change in the tank.

All else fails it doesnt take to long to drop the tank pull the sender and test it with a voltmeter