Intermittent starter failure

[rick8637]

m6bigdog, can you elaborate on senario 2 ? It truly sounds like the bendix sticks. but starter shuts down. I would expect it to contnue to spin/grind if i keep on the key start but it just shuts down with a bit of a clang. until i cycle the key .. then it starts totally normally.

[m6bigdog]

m6bigdog, can you elaborate on senario 2 ? It truly sounds like the bendix sticks. but starter shuts down. I would expect it to contnue to spin/grind if i keep on the key start but it just shuts down with a bit of a clang. until i cycle the key .. then it starts totally normally.

Look at the RealOEM starter exploded view:
There is a fork that is attached to the solenoid that engages the starter drive gear.
Inside the solenoid, is the high current contacts with the battery cable and starter motor stud connections.
The high current contacts make-up only after the drive gear is fully engaged into the flywheel gear, that way the starter motor does not try to run before the drive gear is fully engaged.
If the drive gear and/or solenoid hangs intermittently and cannot reach the full travel the high current contacts will not make-up and the starter motor does not run.
The "clang" you hear could be the drive gear hitting the flywheel gear and not actually engaging the flywheel gear fully, hence the solenoid is prevented from making the full travel.
This could occur when the starter drive gear is warn at the beveled tips and it doesn't slip into the flywheel gear, or just hits the edge of the flywheel gear and stops.

[rick8637]

Now that makes sense! It is not really a bendix! I wonder if there may be corrosion on the starter gear shaft preventing complete engagement. I cant really lube the fork assembly without removing the starter but I last nite I was able to spray the shaft and gear end of the starter and flywheel teeth through the bellhousing and it was quite rusty. I am hoping that it might work its way into the fork assembly with a bit of use. If not Ill be shopping a new starter. That thing is a bear to replace and i wont be going in without a replacement in hand. They are not that expensive!

[m6bigdog]

I would not say the starter is not that expensive at $900-$1,000 for a OE unit.
Core or Sell the old starter to a rebuilder?

Sometimes the starter drive gear gets warn-out(in-a-way) and it will hang engaging the flywheel gear, just that simple.
Replacing the starter drive gear may be all that is required to repair the current problem, but a starter assembly with 100k miles and who knows how many engine start cycles is more reliable when replace with new, as there are other failures possible with the starter parts you have yet to replace (like the solenoid).
Also the labor to R&R the old starter is the same as installing a new starter.
Should you decide to R&R parts within the starter you could quickly spend half the cost of a new OE starter on a few parts and still have an unreliable starter assembly.

IMHO,
Parts only are inexpensive when compared to parts & Labor cost!
Also,
Old Car! new parts always make it better!! Making the Old Car new again..
Old Car! used/refurbished parts may make it better? but most likely, more parts cost and labor in your future!
I dislike working on any cars and I want my cars to be always new, so I go for the new parts option, when possible and just do the labor as a love for the car.

Have Fun,

[shogun]

we have disassembled and repaired quite a number of M70 motor starters, pics here below. My 11/88 motor starter had some plastic gears, that was later changed to metal also on M70, I actually used the innards from a Bosch motor starter for a Mercedes Benz of similar built year as I found one on a scrapyard, pics in the link. Often the solenoid just has to be cleaned, also pics inside http://e32b12.blogspot.com/search/label/Starter
The Benz starter was almost identical, I could use most of the parts. probably from the E class, if I remember correct, only the number of the teeth on the one toothed wheel is different which goes onto the engine,
more pics of the Bosch made Benz starter motor http://infinitier.ddo.jp/e32/images/etc/starter1.jpg http://infinitier.ddo.jp/e32/images/etc/starter2.jpg

http://www.bimmerboard.com/forums/posts/484290/
http://www.bimmerboard.com/forums/posts/462336/

[rick8637]

Shogun-thanks for the links. Its everything you want to know about an 850 starter and more. I personally have replaced this once 15 yrs ago and it was a challenging 1 handed job. I did not remove exhaust to do it. I had more energy 15yrs ago (and i was prob a better mechanic) but I know it can be done. I had replaced it with a bosch SR444X reman. ( i have a huge file of work done) Really cant remember why I had to replace but I am really not excited about doing the job again. Now after getting some lube on the starter gear shaft it seems to be functioning a bit better . I was able to spray it with fluid film thru the access hole in the bell housing and plan on doing it again with the best lube I can find. My car sits alot all winter which doesnt help at all. Even when it fails to engage it doesnt not sound like it is damaging anything so we shall see if i am successful and will report back.