[FC] Coil problem

[Ben's Bus]

Well folks, after the van died on the way home the other night and I got it towed to the garage, things have gotten more interesting.

I noticed that evening that the yellow wire going from the coil to the ignition switch connection in the engine compartment had melted plastic sheathing. Too much juice somehow, I guess. 
The guy at the garage called today and told me it was ready. He replaced the melted wire; said it was not heavy enough for the load and it finally quit. I went to get the van. Started fine, ran fine, then, four houses from home I heard the same "bang" in the engine compartment as Tuesday night and the engine died. I coasted into my driveway and got out to investigate. The HEAVY replacement wire from the coil was intact and not melted. I fished around the wiring for a few seconds. Five minutes later, the van started right up and I drove it back to the garage.

He says he will check the coil and make sure nothing is wrong with it. Any idea what is going on here? I have driven several thousand miles on this engine and its components without a glitch until Tuesday evening.

What would make a "bang" sound and shut off the engine...then allow me to start it five minutes later? I am sure it is part fo the ignition system...

Thanks. Ben