1997 Dodge Caravan major gas leak

My 95 caravan was driving fine. Got in it one morniing and it would crank but not start. Huge clouds of
white smoke coming from exaust pipe. Figured it was the cadalatic converter, and it was. A frined of mine said that he thought it smelled like diesel fuel was in the tank. So he dropped the tank to empty it. Put it back up, but now when I try to start it it just cranks and cranks, no more white smoke but it still wont turn over and now it is has given a few really strong backfires and is leaking gas from all around the tank itself. What do you think my friend forgot to do when he put the tank back that would make it leak that bad?