I had a similar issue on my cherokee recently and I found that the screen attached to the fuel pump had fallen off and was floating around in the tank. I guess it was occasionally blocking the pick up? I pulled the pump, because I had replaced it not too long ago and I figured I got a bad one. As it turned out I shouldnt have re-used that screen. After replacing the screen with a new one, the problem has gone away. Good Luck.