MG Car Repair: MGB Starter Engagement, fender bender, starter solenoid

Question
QUESTION: Howard

Thanks for your help in the past.  I thought I'd go to the well one more time.

I have a 72 MGB roadster.  It was running great and a sweet ride.  No garage queen as I use it often for rallies.  My son recently drove it and had a fairly minor rear end accident damaging the hood, one fender, grille, and bumper.  The radiator developed a leak as a result but I don't believe the accident disturbed the motor or transmission.  I only mention the accident as it is the only thing that has disturbed an otherwise great running car.

I was able to drive the car home and shortly thereafter the problem began.  When I try to start the car, the starter does not engage totally with the ring gear on the flywheel.  I have verified proper voltage by connecting to the actual terminals on the starter solenoid and with a booster starter on it the starter turns but just grinds against the ring gear and doesn't totally engage.  I traded out the starter with the one from my other MG and it does the same thing.

I think I know the answer to this question but wanted a second opinion before yanking out the engine and tranny. Could there be anything else that would cause this symptom besides a worn ring gear?  I can remove the starter and visually inspect the ring gear but don't know what a good one should look like.  Do you have a picture or rendering of what the cross section looks like on a good gear?

I suspect I'll eventually have to pull the engine and change the gear but obviously if it could be something else I want to rule that out first.  Your opinion would be greatly appreciated.

Thanks

Dave

ANSWER: Hi Dave,
The engine stops in only a few places each time you shut the engine down and the teeth of the ring gear do ware just in those places but I never seen one to eliminate teeth completely. This is easily checked by just manually rotate the engine 30deg or more and hit the starter again.
I doubt the fender bender had anything to do with it but I would question your direct starter test.
Did you connect both the (+) and (-) cables to the starter itself?
Before you remove the engine, remove the starter again and with a mirror and a good light look at the teeth of the ring gear. (After you try the 30deg engine turn test) You don't need a picture of what good teeth and chewed up teeth look like as it is very evident. All you need to do is look at the teeth and rotate the crank 30deg and if the teeth are damaged you will see a positive difference.
Howard

---------- FOLLOW-UP ----------

QUESTION: Howard

Yes I connected the booster directly to the ear on the starter flange and the large positive terminal on the solenoid. I think I eliminated the possibility of a high resistance connection.  Especially since it is the same with both starters.  What you said about the engine stopping in certain places and your suggestion about being able to bar the motor over to a good spot and starting it makes sense for the usual case.  

The starter is partially engaging and turning the engine slowly and chattering as it is probably wearing the last of the teeth edge smooth.  Although the engine does turn while this partial engagement is taking place, if I stop and retry I get the same result no matter what the engine position is.  I suspect I will see dramatic wear all the way around the ring gear.  

Please tell me if this is crazy but the ignition switch in this car is a little screwy and sometimes requires a little finesse to operate.  I think I would notice if this happened when I was driving but is it possible that when my son was driving, he didn't get the ignition switch turned all the way back from start to run and drove with the starter trying to engage?  Maybe periodically it has been intermittently engaging when he or I didn't realize it causing wear to the ring gear?

I inspected the bendix on the original starter and it seemed ok.  Would the ring gear be sacrificial or would the bendix wear out first.  Sorry for the long winded discussion but I'd like to not only fix the problem but understand why it happened so I can prevent it in the future, especially if a bad ring gear is only the symptom and not the root cause for the problem.

I will remove the starter and inspect the ring gear as you suggested.  

Thanks

Dave

Answer
Dave, the engine stops in the SAME few places every time so it is impossible to ware out all the teeth on a ring gear. And if the starter were to stay engaged when the engine was running it would totally destroy the bendix in seconds. The only thing I can see for it to be the ring gear is if it has backed away on the flywheel (it is just a press fit) A close examination will show that. Also, did you push start the car and confirm that the engine is good?
Howard