Last week when I started up my 05' GC (4.7) My fuel gauge was reading empty eventhough I had just filled up the evening before. As I drove to work, it slowly creeped up to 1/2 tank. On my way home that evening, it was reading 3/4 full, but than empty again the next morning! Any idea what the problem could be? Seems to fluctuate, but seemingly never accurate.
PITA check is to drop the tank and see if the float is hanging up. If it were not free, it could behave like the symptoms that you describe.
Of course, the best time is when the tank is nearly empty (and you never really know that or you wouldn't have posted here). Unfortunately, I think it's in the top of the tank with the fuel pump. I watched as the dealer dropped the tank to replace the one in my '00 GC Laredo (WJ). He used a jack and it was on a lift because the fuel tank was almost full and the recall had been issued by Jeep. Weight was 20 gal x 7 lbs/gal = almost 150 lbs!
If you do it, the resistance of the tank level float should go from min to max as it goes through it's travel arc. Can also verify that there are no burrs, obstructions or other foreign object hangups in the swing path.
Recommend that you first get underneath to verify that all electrical connections to the tank are tight & clean. May not be very easy, considering where they are (mostly on top). There may be room for a small mirror to look "over the top". Electronic contact cleaner sometimes helps remove corrosion. If you use it, be very
careful, as some of these are highly flammable. Good ventilation is a must.
Please keep us posted. Best of luck and hope it's minor............