Hi vez24. Welcome to the forum. So if I'm understanding correctly, most of the time the starter spins but the engine does not, is that right? And when you said it starts sometimes, that means the engine runs and drives like normal, not just that it spins but won't run, correct?
If that's the case, the starter drive gear isn't engaging the ring gear on the, ... Well, depends on whether it has an automatic or manual transmission. The next time it doesn't crank, grab the serpentine belt and use it to rotate the engine a little. Turn the engine in the same direction the tires turn when you're driving forward, then try starting it. If it cranks and runs, suspect a spot on the ring gear where the teeth are worn off or broken.
Wednesday, May 5th, 2010 AT 4:18 PM