Astro 4.3

My 2000 Chevy Astro just turned 100k. Today it will not start. At end of key turning I get a puff of exhaust from air intake at mass air sensor (intake off) Timing belt jump? If so are valves at risk?

doesn’t have a timing belt, it has a chain. I’m assuming its the 4.3 v6. check fuel pressure and spark before assuming this.