Starter turns but won't turn motor

[Mkeenan 2]

Hey,

So I bought a 69 351 2v with the fmx, when I test drove and the day I bought it, it started great. Now two days later when I turn the key it sounds like it's grinding a little and not turning the motor over. I can put it in gear and roll it 15 feet then try and start it and it usually starts with no problems. I thought maybe a flat spot on the flex plate but it has done it 6 or 7 times in a row now. I pulled the starter and everything looks normal but I'm not sure. All my connection are good the battery is good, the starter was tight. I read a few things about the difference between auto and manual transmissions the only numbers I can find on it are DOOF-11131A. And is normal to have what looks like someone used a grinder on the end of the shaft near the bearing. New to old school stuff but not new to turning a wrench.

Thanks

Keenan

[Footcutter11 23]

Auto and manual starters are different.  I have a manual, but the flywheel I have had an offset that required an auto starter.  Might be a place to start making sure your offset is correct.  When I put in the manual starter I had very much the same symptoms.

[Max Power 74]

When you shut off your engine, the engine will almost always stop in one of 4 places. That's because engines will stop on a compression stroke, and V-8 engines fire every 90 degrees, thus the 4 locations. Over the years, the flywheel or flexplate will wear the ring gear teeth in those 4 locations. I think your starter is probably fine, your have worn or stripped teeth in the ring gear. When it fails like this, pull the starter and inspect the ring gear. It is probably worn in that spot. The short term solution would be to shut the car off while still in drive, the resistence from the drivetrain will have the motor stop in all the other locations than just the 4.

 

The fix, of course, is to replace the ring gear. No small task, as you have to pull the tranny. Since engines are balanced with harmonic dampers and flywheels as part of the rotating assembly, make sure to have a replacement flexplate balanced to your old one.

[Mkeenan 2]

Thanks I'll have to see if stopping it in gear helps.

[RPM 1,190]

Hey Mike, welcome to the friendliest forum on the planet! How bout a little history on your Mustang, some pics and where you live?

[Mkeenan 2]

So I think I got it fixed. I pulled the starter and inspected the flex plate I couldn't find any spots where the teeth were worn or missing. I did however notice that the shaft bearing on the starter was in worse condition then I thought. So just out of curiosity I put the starter in a vice and hooked up a battery charger to it. When power is applied the starter gear is not fully sliding out and there is a lot of unusual vibration. Went down and bought a new starter, put it in and it fired right up. I drove it around for a while shutting it off then starting it back up. It hasn't done it since.

[Max Power 74]

So I think I got it fixed. I pulled the starter and inspected the flex plate I couldn't find any spots where the teeth were worn or missing. I did however notice that the shaft bearing on the starter was in worse condition then I thought. So just out of curiosity I put the starter in a vice and hooked up a battery charger to it. When power is applied the starter gear is not fully sliding out and there is a lot of unusual vibration. Went down and bought a new starter, put it in and it fired right up. I drove it around for a while shutting it off then starting it back up. It hasn't done it since.

Well, that is best case scenario. Excellent.