Battery cables could be loose, battery could be bad, starter could be bad, starter solenoid could be bad, ignition switch could be bad. Turn on the headlights and try to crank the engine. If the headlights dim or go out look at the cables or battery. If they stay bright look at starter, solenoid or ignition switch. The neutral safety switch or clutch petal switch could do it too.
installed wrong or bad fuel pump
check for cats
check for bad crank sensor!!
mine did the same thing i replaced the crank sensor and it runs fine
it could be weak spark plugs.
hi i have a 01 vw jetta i just got it back today from the dealership my car would turn over but not crank and it was the mass airflow the replaced it and restarted the computer on my car and it runs great !! it only cost me 450 to fix it
Crank shaft
Things to check. Does it crank? If not,battery, starter, If it dies crank, fuel pressure, spark, check engine light codes.
Will it crank? If not, you may have thrown a rod.
cooling fan relay short or bypassed or defrost or ac selector on
The crank shaft sensor may have died and the engine controller is using other sensors to keep the engine operational in "limp" mode.
Your question is very confusing. If the car runs then it has to start. Please clarify.