I'm on my third new Bosch starter in about 2 years in my '78 240D. The starter drive gear on the starter I just removed is basically demolished. I checked the ring gear on the pressure plate and the function of the starter mode on the ignition switch. Everything appears to be OK. Does anyone have any thoughts about why the starter is "hanging up" i.e. continuing to engage after the engine starts? Ken Taylor

 

You said you checked the Ring Gear. But, this is my thoughts.

What I have seen on other Ring Gears is that while the teeth may look good if you reach in and feel the sides of the teeth; especially on the Starter side of the Ring Gear there is mush out deformed metal that sometimes does not make it easy for the Starter Gerar to mesh.

They need to be filed or ground back to the origional thickness/width of the Ring Gear.
It also could be that while the Ring Gear has teeth that they are worn thin in the area where Starter Gear makes contact.

Another problem can be that if your Engine has a starting problem and requires an abnormal amount of Cranking of the Engine starter; equals abnormal starter wear (remember unless you have a leaking Rear Main Seal the Starter and Ring Gear get no lubrication).

Members of the other Forum I hang out at have said it is best to pay extra and get Bosch Rebuilt Starter. As, there have been a lot of them that have had to return Starters under warranty from the Local Parts Chain Stores.

Posting a pic of the demolished Gear also might help decide what is wrong.

 

I am having a similar problem to the one posted. I had an Auto-Zone starter for four years which needed to be replaced. I replaced it under warranty and put the remanufactured one in. A month later one day the starter wouldn't stop spinning. The engine would be running but the starter would still be spinning away. When I shut off the engine, the starter would continue to spin away and wouldn't stop and the engine wouldn't start when I turned the key. The only way to stop the starter was to disconnect the battery. After several removal and replacements of the battery cable to the battery terminal the starter finally stopped spinning - maybe it burned out. The battery terminal got melted in spots because of the sparks when the I touched the cable to the terminal.
So I took off the Auto-zone starter and returned it to the store under warranty. I put the new one on and it worked fine for a few starts that day and then did the exact same thing. I'm wondering if I'm having very bad luck with the starters or if the ignition switch could be the issue because the car is a 1982 240d and that's a lot of years of starting. Any ideas?

 

Ralphinsl it sounds like your starter solenoid is sticking. Might be the same for kftaylor. That is usually caused by a high amperage draw, very tight engine, dragging starter,and misaligned starter to ring gear are common causes for that failure. Start by checking the solenoid itself, might be that it is under sized, and causing the contact disc to melt and weld to the terminals. Starter rebuild shops would have the heavier solenoid and quite a bit cheaper than a replacement starter. kftaylor you also might want to check crankshaft end play if it's excessive it might cause the bendix gear to be destroyed. Also check your armature bushings. Side float of the starter shaft will cause it to hang in the ring rear

 

Thanks for your suggestions, which I've printed out. The car is currently stuck in my garage and I've got a replacement starter on order, but also wondering if maybe I should take it to a rebuild shop rather than rely again on remanufactured starters under warranty from Auto-Zone or Pep Boys. I've also ordered a new ignition switch but I replaced the lock and tumbler four years ago when the lock stuck resulting then in a ruined starter because it didn't disengage. I'm thinking that possibly the 32 year old ignition switch could be worn out. In any case, the current starter needs to go. Thanks, Ralph

 

This is hard to say with out being there.

A real Bosch Starter Solenoid can be had for about $90 on the Internet and an aftermarket Solenoid can be $10-12 Dollars. I would assume the same quality issue is there for the Overrunning Clutch that engages the Ring Gear.
So the Auto-zone Starter rebuilt with generic parts could be the problem.

As I mentioned in my other post if the Ring Gear Teeth are bad it is possible for them to cause the Overruning Clutch to stick in place; but that is not common.

To see if is the Igition Switch causing the issue you could hook up a Volt Merter or test light in the Wire fromt he Igniton to the Starter Solenoid. If the Starter stays engaged after you turn the Key to run and you still have voltage ther or the light is still on it is an indication that the Ignition Switch and or the Steering Colum mechanism that turns the Ignition Switch is having issues.

If it remains engaged and there is no Electricity going to it you have I believe you have a non-electric issue causing the Starter to stay engaged. Meaning it is unlikely the Solenoid is not what is holding the starter in engagement.

 

I went through the work of replacing the ignition switch assuming that must be what is keeping my starter engaged and it made no difference. When I connect the battery cables, there is the same spark and the starter resumes spinning but does not engage the flywheel. The next thing I will do is see if that little wire on the starter from the ignition has power when the key is off.
The mechanics I have worked with believe it is the starter I got from Auto-Zone, however, the other starter I got from PepBoys does the same thing. I've had the one which is off the car tested at AutoZone and it tests OK. I am willing to try a Bosch remanufactured starter but if that is not the problem I'm stuck with another starter.

 

If you cannot deal with it Yourself you could see if there any Private Auto Electric Businesses (I am not speaking of one that just installs Auto Sound Systems) in your area that rebuilds Alternators and Starters. And refer the problem to them.

Most Mechanics troublshoot and replace Parts. They do not rebuild parts or always know why parts fail. A place that actually rebuilds Starters sees the innards and has a better idea what causes what problem.
They also need repeat business so they take care in what they do.
In any even a Phone Call to a local Starter Rebuilding shop would not cost much.

What is unknown to Me is if all 240Ds use the same Starter Motor or there is dimensional differences.
I know when I look up Mercedes Part Numbers there is often a notation that has beginiing with and ending with certain Engine Numbers or Chassis Numbers and that can be witnin the same Model Year.

 

Today I am going to remove the Pepboys starter and reinstall the latest starter from Autozone. Hopefully it will work, at least initially. I can take the Pepboys starter back under warranty, which is the one that lasted one day. I installed a new ignition switch, which made no difference; the starter remained engaged - that is drawing battery power and spinning while not engaging the flywheel. When I disconnected the ignition wire to the starter, it still drew power. It's hard to believe a starter, supposedly remanufactured, could last only one day. The prior one from Autozone lasted one month. After this, I will have to buy a Bosch remanufactured starter or take one of the two starters I have to a shop that rebuilds them.

 

Check that the battery cable where it hooks to the starter that it isn't touching the heavy wire, or bolt that goes directly into the starter if it is that will cause the starter to spin bypassing the solenoid which would not engage the bendix gear. To see exactly what happens when the starter is engaged, or bench check a starter for yourself. Hook a set of jumper cables to the battery with the neg. side to the starter frame, and the pos. side to the solenoid battery terminal. With a screwdriver that you don't care about touch the small terminal to the battery terminal while hanging on tightly to the starter it should act the way it does in normal operation . Then go directly to the bottom heavy terminal from the battery terminal, you will see what you described in your last post, the starter will spin, but no gear extend. I think you have your battery cable touching the heavy wire on the bottom of the solenoid. That wire goes directly to the starter brushes making the starter stay energized, but not the solenoid.