Looking for some input. its a 2004 4.0 4x4. I just hit 80,000 miles. driving today the gas gauge went from half tank to empty and the light came on. I thought it was a leak or something. as I pull into the gas station, the needle jumps back up to half tank. as I pull out it drops to empty again, then back to half tank. the truck sat for a few hours then i started it up and backed out of the driveway, the gas dropped to empty and the check engine light came back on. on my drive, the gas went back up but the check engine is still on....

any suggestions?????

thanks

 

Sounds like the sending unit. Since I haven't had to deal with one in my truck, I will assume that it's in the tank. Can't tell you how to test it though.

 

It could be the anti-slosh module behind the the gauge cluster, or your float may have a tear. My 91 was doing similar things to the gauge after i had swapped out to a tach unit, I just changed the anti slosh unit from original and all is good.