damn man that sucks..... my trooper did something simular when one of my injector wires were pinched and grouding out on the air lid. It was disabling the fuel pump.
I'd suspect its a fuel pump problem. Check the wiring behind the fuel tank, I've have to replace alot of my wiring back there, and from what I hear its a pretty common problem with first gens.

I too had that backfire-fire when my fuel pump wasn't working and I dumped some fuel in the tb.

89 trooper, tera low t-case gears,5.38's, 3" indy4xsus lift3"body lift,safari snorkle,warn winch,custom bull bar,custom rock sliders,warn hubs,35x13.50r15,custom rear bumper trooper pics