Starter motor problems
 

The starter on my 87 420 slips from time to time. 1 out of 10 times it misses. As best I can tell the solenoid is engaging the bendix gear and the starter motor turns but the engine does not turn. You can hear the sound of the starter winding up to high RPM's. Almost as if the bendix gear is not meshing with the flywheel. I took the thing apart and cleaned and greased it. The bendix gear seemed normal - catches in one direction and freewheel in the other.

It is my conclusion that the bendix gear is slipping or not catching at all. If the solenoid was not working then the starter motor would not spin at all - would it? Is it possible that the solenoid is able to apply power to the starter motor and not engage the bendix gear.

I invite any and all opinions on this subject.

While you are going about this in the correct manner by really analizing the problem at hand, if you have it narrowed down to the starter, I would just replace the starter. It comes with a new solenoid and a warranty.

The reason for this is the labor is not cheap! You don't want to take out the starter two or three times to fix one problem.

if it sounds like the bendis at least contacts the fly wheel but does not turn it there is a small chance that you have worn out teeth on the fly wheel. but some how the the darn thing always manages of stop in the same place so it would fail more that 1in 10 times. i dont know that the starter would not work without the sloenoid working. try tapping the starter with a hammer while cranking it that works some times and is indicitive of stuck parts.
good luck

I think the bendix is sticking on the shaft - before you buy new motor assy - try cleaning up the bendix assy and look at the ride areas - you might want to clean the ride areas rubbing with 1000 grit sandpaper to clean up. then put a little white grease on the ride surfaces and try that. Of course the easier way would be to buy a new bendix to try. It appears that as the starter turns - the bendix does not get thown all the way out to engage - that is why I think it is sticking. DO NOT HIT THE STARTER WITH A HAMMER. YOU CAN BREAK THE FIELDS LOOSE FROM THEIR EPOXY AND DESTROY THE MOTOR. That is all I can suggest.

Had the same thing happen, it turned out to be the bendix. On the bench it seemed okey but it couldn't handle the load of turning an engine, sometimes:rolleyes:

I was able to buy just the bendix from a auto electric shop. I needed help, there's a special clip that held it on. I just brought the pieces in and they just took the clip off for free, I could get it on by myself.

Thanks for the replys. Jim I think you had the same problem as me. I know the ring gear is good since I just rebuilt the transmission myself. Since I was there I decided to have a look at the starter and ring gear cuz it had acted up on several occasions. I completely disassebled the started cleaned, lubed, and checked every inch of the thing. There was a lot of road grime on & in it so I thought that it was sticking. But I think it is the bendix gear itself.

Im going to do exactly what you did. Replace the bendix gear. Ill let you know if that was the right decision.

dpetryk,

This is a problem I encountered with my 240D, and I had to have the ring gear replaced. The reason you only get a failure every so often is the crank stops near the top of one of the pistons' compression strokes. Multiple pistons gives you multiple places to stop on the circumference of the ring gear. Consequently, if the starter engages an ok spot, the engine starts. If it engages a worn spot, you can get a nasty metallic clank/grinding sound, and the engine won't start. The only answer in the case of a bum ring gear is a new one. If the pinion gear on the starter is worn, you need a new one of them too or the starter won't work for long - the same mechanism that wrecked the ring gear originally will wreck the next one.

Hope yours is not the ring gear, as that is a greater pain to replace than the starter bendix. Jim

Let me say it again. The ring gear is good. I had it off during a tranny rebuild. Not missing any teeth. No marks, no visible wear, its good all the way around, looks like new.

When the starter does slip, the noise it makes is smooth sound, no grinding at all. Just the sound of the starter turning at high RPM's. Similar to what you would hear when bench testing it. It sounds like there is no ring gear on the engine at all. No contact, no meshing, nothing. But of course there is. So I can only conclude that the bendix gear is slipping, or its not engaging, but I can hear the solenoid "clunk" so I assume it is working.

I appreciate your input. Thanks

One of the guys at the office just had similar symptoms on his 450SLC. It was the bendix not engaging, actually I think it was trying to engage but was hanging up. The bendix had been pulled off several times and lubed, which help for a short period before hanging again. Since this was still the original starter, he opted to replace the complete starter rather than just the bendix.

Thats the plan at this point. Its not too much fun to pull the starter. The worst part is hooking up the wires.