Starter spinning but the engine will not Crank
There are few possibilities that can cause the problems:---
The starter drive on your starter is faulty.
The starter drive is not engaging the flywheel to crank the engine.
The flywheel issue.The flywheel has some cracked or broken teeth that stops the starter from engaging.
Understand the starter system of the vehicle:---
On some starter the solenoid is mounted on top of the starter.
Now When the ignition key is turned to ON, the solenoid paths current to the starter motor and at the same time pulls a lever that forwards the drive gear mechanism out so it will engage the flywheel and crank the engine.
But when solenoid is weak or damaged, it may not be strong enough to overcome the spring tension that retracts the drive gear. So the starter spins but doesn't crank the engine. In your case this might be happening and that is what causing the problem.
On other type of starter assembly the solenoid is mounted remotely. In this starters when the starter motor starts to spin, it ratchets out so the drive gear will engage the flywheel and crank the engine. In this case if the drive mechanism is damaged or hung up, the motor may spin but not crank the engine.
In any case the starter motor has to be removed out to inspect the starter.
WHY ENGINE WILL NOT START:
This are due to few possible reasons.
What exactly any working engine needs to start?
Engine requires sufficient cranking speed, good compression, adequate ignition voltage (with correct timing) and fuel (a relatively rich air/fuel mixture initially). So whenever an engine is not able to start, any of the following is not performing.
If the engine won't crank, you are probably dealing with a starter or battery problem.
If an engine cranks but refuses to start, it lacks ignition, fuel or compression.
When the engine cranks ordinarily but won't start, you need to check ignition, fuel and compression. Ignition can be checked with a spark tester or by positioning a plug wire near a good ground.
No spark? The most likely causes would be a failed ignition module, distributor pickup or crank position (CKP) sensors.
