Originally Posted by
RichR
Sounds like the starter motor pinion gear has jammed onto the flywheel, so it can't turn it when you try to start it, and you can't push start it, because the flywheel's jammed. Probably due to a flat battery or poor connection at the connector by the headlight allowing the solenoid to come part way out, but not properly. Or it could be a lack of grease in the solenoid so it's sticking.
Take the starter motor off. You'll probably find the pinion retracts when you loosen the bolts (ie giving it room to come free). Check the starter works properly by clamping it in a vice and applying power to the solenoid tag (body of the starter to negative on the battery)- the pinion should shoot out, but the starter won't turn unless you have run 12V to the main starter terminal as well. Do this next if the solenoid does move the pinion properly.
Then make sure the battery in the car is fully charged, check the connector by the headlights, refit the motor and try again.