Remove the starter motor and inspect the teeth on the ring gear and the starter drive gear. If they are okay, either the starter drive's over-running clutch is bad or the flex plate is broken around the center where it bolts to the crankshaft.
You can also try turning the engine a little by hand, then try starting it. If that works, suspect worn ring gear teeth.
Friday, March 9th, 2012 AT 6:30 PM