Freewheeling starter?

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Joined
Feb 16, 2015
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Location
Granbury, TX
My Car
1971 Mustang Mach 1, 351 4v, C6, Holley 650
Occasionally when the starter turns more than a few seconds (not so much now since the new fuel pump) it will quit engaging the engine and freespin with an amazingly loud whirring noise. This is my assumption of what is happening based on my limited knowledge but fairly certain. Why would this be occurring and do I need to worry about this potential problem and/or fix it?

btw; I'm still relatively new to this site but have really been impressed with the professionalism and at the same time camaraderie, support and patience from all the mods and members. Really glad to be here.

Eric

 
This can be caused by a few different things. A common one is when the engine fires on one or two cylinders, kicking the bendix (starter drive gear) off the flywheel or flexplate teeth. Others are worn teeth on either the flywheel/flexplate or bendix, debris keeping the bendix from fully engaging, the bendix actuator lever binding, worn out brushes keeping the starter from spinning fast enough, and worn bearings/bushings in the starter.

 
In addition to Don's advice,

If you can get the car lifted enough to crawl under, you can remove the inspection plate to check the teeth on the flywheel easy enough. While you're under there, you'll need a friend to manually rotate the engine in order to see all of the teeth.

Then you'll want to check your start cables and solenoid. Make sure you have a minimum of resistance through the circuit. If there's a significant increase of resistance in the cable on either side of the solenoid (differing from the other), you might have a bad cable.

If the resistance rises or voltage drops while trying to start it and the starter motor does what you're saying it does at the same time, it might be an issue with your battery and/or solenoid - especially if the solenoid is getting hot while cranking.

If the flywheel has all its teeth and the cables, solenoid and battery are all in good shape, I'd think strongly about replacing the starter - the "Bendix motor" is most likely getting tired and will eventually just fail altogether.

Hope that helps.

 

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