My jeep had a bad fuel odor outside, sometimes inside, and it turned out to be the gasket between the fuel tank and the fuel sending unit that is inside the tank. There was a factory recall on it back in the day. Some people have said the dealer will change it still but I went ahead and did it myself. The gasket is is $15. If it's strong in the rear this could very well be it. It's a known problem. You have to drop the tank and swap out the gasket. It's not a difficult task.
93 YJ, 4.0, 4.5" suspension, 33x13.5 Pitbull Rockers, Custom scratch and dent job...
05 WK, 5.7 Hemi, Quadra-Drive II