It's a '91 300SE with the 103 6-cylinder.
For about 2 years we have seen an occasional starter malfunction. Happens only when the engine is cold, and only happens about once or twice a week. I hit the starter, and starter runs, but does not engage the flywheel. There is absolutely no grinding noise like we used to hear on the old Chevys when the starter gear was chewing on the flywheel teeth. once I had the presence of mind to hold the key on for a few seconds, and starter made a nice smooth sound, but the motor did not turn over. I turned it off, retried, and all was normal.
Battery is great, and it starts totally normal when it does engage.
I had the transmission off last year to repair a seal leak, and checked out the flywheel teeth - they looked really good, with only very minor wear at the three "stopping points". I made a decision to not replace the flywheel it looked so good.
Last year I pulled the starter out and dis-assembled and cleaned it up. The gear teeth looked good, and showed no real signs of abnormal wear.
Problem has not gotten worse for a year, but still happens on a routine basis. It always starts on the second, sometimes third, try; but makes me nervous.
My take on this is that the starter drive is not travelling fully out far enough to engage the flywheel, due to maybe binding or maybe low voltage/high resistance in the starter. other possibility might be starter gear clutch is slipping, but it seems that would occur more often/get worse.
I guess I should just get a new starter - you guys have led me to some great pricing on some other posts - but I am just curious about this behavior. I always felt I could diagnose anything given enough time, but I never saw a starter do this; they either click or grind, or do nothing, and it always gets worse after a couple of YEARS!!!!

Any suggestions????? Thanks.

S-Class Guru

p.s. note this is my 3rd post, and my first original post. But I have read the forum for years. it's a great credit to you guys that I have always been able to find answers to everything I wanted to know by just searching. But you guys looked to be having a lot of fun, so I finally had to join in.

Yeah, it's the starter drive......my '84 380SL is going in on Monday to have a new starter put in for the exact same problem. I opted to have a mechanic do it.....It's not worth me laying out under the car in the snow when my mechanic will do it for $75:p

__________________
Old age and treachery will allways overcome youth and skill!

1993 S500
1984 380SL