Starter won stop!

[SamuraiJack]

I have a 79 240D. I started it up today and heard a whining sound under the hood. When I shut the engine off, the whine continued. It was the starter motor continuing to run. I had to disconnect the battery cable to get it to stop. When I touched the cable back to the post, I got a big arc and the starter motor started (but wasn’t turning the engine?). Any ideas on how to trouble shoot this? Is the solenoid replaceable? Is a relay stuck? A new starter needed?

Thanks!

[snipsa]

I have encountered many starter failures with these cars but have never seen one go where it is stuck on and not turning the engine. But the symptoms seem to indicate the problem is within your starter since the starter pinion should jump out to turn the engine whenever the starter is running. I have always just replaced the entire starter even when I was sure it was only the solenoid. I believe the cost difference was not worth the bother when I checked. I usually get the Autozone lifetime warranty starters and have never had to re-do a starter yet.

Also, make sure you get the heavier duty starter that was used on the later turbo 123's I don't think the cost was any different and they should all bolt up the same. I did this on my friends 240 and it was a huge improvement over the old one before it quit. I dont know if its geared differently or what.

Anyway, good luck.