1979 240D Starter/Ring Gear Problem
 

I have a 1979 240D with an odd Starter/Ring Gear Problem. 10 months ago, I replaced the starter with a Bosch rebuilt unit. Worked well, and the starter began dragging.

One month ago, I exchanged the starter under warranty, and it worked well for 15-20 starts. After that, the started would begin to spin the engine, then within 2 seconds, the engine rotation would quit, and the starter would continue to rev up higher and higher, while the diesel engine quit spinning.

I again warranted the starter, only to find the new starter exhibited the same problems as the second starter. The only thing I can think of is the ring gear is slipping on the flywheel. I rotated the engine by hand, and looked at the ring gear through the starter mounting gear, and the teeth look fairly good, and the ring gear does not appear to be cracked or broken.

Has anyone face a similar situation? I appreciate any help.

Update
 

I looked at the flywheel and starter ring again this evening. The ring gear is flush with the flywheel at the engine side of the flywheel, opposite the clutch side. It appears the flywheel has a machined lip, behind the ring gear. FOr the guys that have replaced the ring gear on the flywheel, is the ring gear supposed to be seat flat against this machined lip, and have 1/8" - 1/4" of the flywheel exposed on the front side?

Second, is the ring gear made out of softer material than the flywheel? I'm wondering if I purchased a new ring gear, if the flywheel will be slightly undersized now. Thanks for any help. http://www.peachparts.com/shopforum/images/smilies/rolleyes.gif

The ring gear is supposed to sit against the lip on the flywheel.

The ring gear is made of harder material then the flywheel.

Undersized where the ring gear sits?
Not as long as the ring gear did not spin on the flywheel.

Your pic doesn't work.
At least not on my computer.

I don't think there is any way that you can spin the starting ring gear on the flywheel. I thing the Bendix drive on the starter is where the problem is. When you replace the starter, are you replacing the solenoid also. If it is slipping, it would slip all the time. If it turns the engine for a few spins and quits but the starter continues turning, then the Bendix assembly in the nose of the starter is not staying in gear. It is the magnetic drive of the solenoid, (on top of the starter) which kicks the drive of the starter into the starter ring gear and holds it in gear. When you release the key from the start position, you pull the power from the starter and the solenoid. I would suspect you have a wiring problem from the switch to the solenoid. I think your problem is much the same as quite a few members of late whose diesel engine starters just up and quit. No power from the starter key to the solenoid. I had that problem on my 85 300D and now on this 83 240D which I converted to a 300D. So I rigged up a bush button starter along side the switch and it works well and is simple to do.

To fit the toothed ring on the flywheel you need to heat it up... I think it is unlikely that it is slipping but then you never know.

Paint some witness marks on the ring and the fly wheel to see if there is slippage. I'm guessing this will be necessary to put your mind at rest. Paint several marks so you can easily check - rather than spending ages trying to find that one bloody mark you made!

In case you haven't found it there is a little access plate right at the bottom of the engine that can be unscrewed from the bell house on the transmission.

If you need to turn the engine by hand turn it clockwise (when facing the engine) with a 27mm socket.

Then re-read junqueyardjim's response!

Thanks!
 

Thank you Army, junqueyardjim and 1960mog. I will try your suggestions tonight. I have already removed the infection plate at the bottom of the bellhousing, so I can watch what occurs when I re-install the starter. Currently it looks like the ring gear is 1/8" away from the machined lip on the flywheel, instead of fitting flush with it.

After my last post, marking the flywheel and ring gear occurred to me, but I hadn't discovered the inspection plate yet, and got lazy not wanting to remove and replace the starter multiple times. Now I will have the starter mounted, mark everything and watch what happens.

The reason I was asked about the metal hardness is that if the darn ring gear is slipping, I hate to buy the ring gear if the old one has spun and taken down the flywheel.

And to clarify, the starters I've used are Bosch certified rebuilt starters, so hopefully they are decent quality. The starters where purchased assembled with new solenoids and everything complete.

Junqueyardjim I hope you have the best solution. I will set up a jumper wire directly from the battery to the terminal and see if that cures the problem. Thanks again to all, and I'll let you know what I find out.

Problem Found
 

After following your recommendations, the problem has been found. The ring gear is spinning on the flywheel. I marked a location on the flywheel and ring gear, bumped her twice, and the mark for the flywheel was nowhere near the ring gear mark.

So I had the better half come out to crank is while I watched under the bell housing inspection plate. After she chewed me out, for finding out I used her favorite nail polish to mark the flywheel, she cranked the MB OVER. The darn ring gear is spinning on the flywheel.

I'll pull her apart this weekend, and I think I'll weld the gear to the flywheel. I need the car for monday, and money's tight, so I'll give this a whirl. I'll post to let you know what happens.

Thanks again.

I'm glad to read that others have those domestic moments of bliss too!

Bummer about the flywheel...

I think you'll be better off replacing the flywheel. If you have an automatic gearbox the flywheels for that configuration are quite cheap. I'm sure someone here can help with one...

But please be aware that some people say you should replace the flywheel bolts as a precaution. They are not cheap... (for the price of bolts)

You need a good quality 12 point 12mm socket to take out the bolts...

I don't think welding the ring gear to the flywheel will work on the diesel. I did it on my M115 (4 cylinder gas) but it has no where near the compression your diesel has.

Ring gears are available but you have to remove the flywheel to get proper access. MARK the flywheel and the crank before you pull it apart. The units are balanced at the factory and this helps avoid any future vibration.

You should also mark the flex joints to their respective flanges.

When you have the ring gear separated from the flywheel take it to a machine shop and have them measure the diameter to ensure it will accept the new ring gear.

Buy the wife a new bottle of nail polish and pick yourself up a yellow marker crayon while you're at it. Tell her, "Ya know, Hon, I liked the color so much on you I just wanted to have something on the car to remind me of you to let me know what I'm missing when I'm working on the car and not spending my time with you".;)

I don't think welding will work.
The ring gear is steel and the fly wheel is cast iron.
Get a used fly wheel and have it balanced against the old one.
Or just install the (new) used one and hope for the best.