[85Mustang50]

So, my friend and I replaced the starter lock tumbler switch (or whatever it's specific name is) and went to turn the 5.0 over, but it wouldn't start! The engine was free, we spun it by hand, but for some reason the starter would spin, but would not engage. We decided to pull the starter and replace it with a reman starter from Napa, so we bought the starter and threw it on. As expected, the 5.0 started right up, but began to leak fuel out of a cheap in line fuel filter, so we shut it off. Just to double check the problem, we went to restart the car, and the new starter has the same problem as the old one, it's just spinning and doesn't sound like it's engaging the flywheel. The Mustang is a stickshift, so I'm not sure if a clutch position switch would be a problem, since the clutch was depressed fully, and the starter was spinning.

What could cause the starter to spin and engage one minute, but then spin and not engage the flywheel the next?

Please help!

[BlueStreak03]

Try rotating the engine over by hand 90-180 degrees and crank. It sounds to me like maybe there are some teeth that have been ground completely off the flywheel. If that's the case then the only thing you can do is drop the tranny and replace it. If it still doesn't engage after rotating it by hand then I would take a long look at the starter solenoid. I don't know for sure if it is piggybacked on the starter for that year of the car.

[meangreen92]

You can have a new ring gear installed on the flywheel, as an alternative to replacement.
I didn't believe it either, until I saw it with my own eyes...