Could be a number of things.
Basics to check:
1. Does the engine turn over? If no, check battery cables, hit starter with a hammer, bypass starter solenoid with a screwdriver......
2. If engine turns over but doesn't fire up, watch the instrument cluster while cranking, there's a yellow arrow, that should extinguish shortly after turning the key to start. Watch the harmonic balancer for wobble while having someone crank the engine. Give the gas tank a whack, could be a fuel pump. Give the relays on the right firewall a whack. Check engine ground wire connections......
It could be any number of things, start with answering the above and we'll help get you going.
JJ
