1986 Chevy Truck Almost Dead!?

Like I said I have a 1986 Chevy Scottsdale truck. It's not a daily driver and it kind of just sits in the driveway, so I decided to turn it on just to "warm it up." I left it running for about 15 min, turned it off and it backfired really, really LOUD, the engine sputtered for about 10 seconds before it completely shut down and now it won't start at all. What could have happened to it? I like the truck and it comes in handy so I would like to fix it. Thanks to all who respond.