the first thing I would check is, fuel, spark, coil, ignition module
Cranks is the motor turning over, But cranks and won't start means either you no fuel or no spark or both.
are you getting spark?
An engine which cranks but will not start is not receiving enough fuel or has no spark. A clogged fuel filter or bad spark plugs often cause this problem.
engine cranks over but will not start.
check the crankshaft sensor
Sounds like you have a dead battery.
If it just cranks and cranks and cranks then it's likely fuel pump. If it died and it won't turn over anymore, likely alternator.
On one had you say it cranks and then you say it won't turn over. Which is it? If it cranks, then that means it IS turning over but just won't start. If it won't crank then it is NOT turning over. We need to know which it is to determine what may be causing this. Repost this with a better description of your situation
engine cranks but wont start means one of these things.. Air, Fuel, Spark, or compression
could be disdributor
if there is backfire, check the exhaust restriction....