i know this is a pretty big problem for alot of j owners. It seems that this problem can stem from a lot of different sources. I had the problem and i almost positive i have fixed it. If you check your ground wire that attaches to your battery tray mine was half off almost not attached anymore so i made a new ground from the engine block to the battery tray and i have not had the problem since. Try it on yours if you have the problem and it may fix it.