if it backfires it could be timing or else you have it flooded from trying to start it. You didn't say if the engine is carb or fuel injected. If it is carbed, let it sit for awhile to let the gas drain out of the carb. If it is fuel injected then it is probably timing. year make and model of vehic and millage
You will know if your car has jumped timing by the way it starts up. If the engine is slow and sluggish, it could be a sign of jumped timing. Also listen out for strange noises coming from the engine or if it backfires, it is likely that there has been a change in the timing sequence.
It could be your timing is off or your timing chain needs replacement.
timing or carb
Sounds like the timing is off.
Valve timing off, timing chain jump.
Check your timing and your vacuum advance.
That sounds like your timing is off. Adjust it at the distributor cap with a timing light.
i would look in to having the static timing checked.(ignition timing) you may have crossed sparkplug wires or the timing is simply way off,among other things.
Your timing belt has probably worn out, or broken, and has jumped timing.
check your timing
Perhaps timing chain has jumped
Have you checked the ignision timing. Check the firing order as well