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Old 09-24-2019, 12:57 PM
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gmog220d gmog220d is offline
There is Life After VW!
Join Date: Apr 2006
Location: Albuquerque, New Mexico, USA
Posts: 856
Originally Posted by inzgary View Post
Here is one similar instance I found: Pre-Chamber Ball Came Loose
That was a 220 so the non turbos also had the same pre chamber design. Add going 70 mph down the highway and the pressures going in and out of the pre chamber are likely high enough to blow the tip away. My theory is that is caused by a streaming injector. The metal ball starts burning, breaks loose, and rattles around ultimately creating a check valve of the pre chamber.
That's my thread linked to above. Given my experience I tend to agree with inzgary and others that your problem, Joe, started with a leaky injector permitting too much fuel to enter the pre-chamber. As I came to learn, thanks to other helpful and patient members on this form, too much fuel injected will burn things up, like causing the ball to come loose, deforming the glow plug tip, etc., and perhaps eventually leading to a major blow out like you experienced.

My troubles were caused by my mucking around with the IP governor. I ended up with a rich condition and it took 2000 miles of driving to reach the point shown in my thread. What happened to your engine is an extreme version of what happened with mine. In my engine, because the trouble linked back to the IP, every cylinder was affected, but it was #4 where things reached a breaking point. I got lucky - the pre-chamber did not come apart and drop pieces into the combustion chamber. My situation played out more slowly because the problem was not caused by the injector itself, the rich condition in my engine was lesser than it would have been if it were the injector dribbling into the pre-chamber.

I am embarrassed to admit that my '74 240D is still off the road, the IP still sitting on the bench waiting to be installed. Our "new" property in the mountains has caused a shift in my priorities, and wrenching on my extra vintage car has moved way down the list. At least it's sitting in a garage, protected from the elements. I think I'll get back on this project in the near future, though. I'd like to drive it!

Anyway, I believe that injector maintenance should be a high priority for these engines, especially in a car that's "new" to us. Pulling the injectors and having them checked and repaired is one of the first things to do, unless you know for certain the injectors have been worked on in recent past. I also like to pull them every couple years and have them popped by the local shop. I never had a problem until I messed up the IP's fuel output. Lesson learned.
- Greg -
1973 220D, The Prodigal Benz
1974 240D
1996 E300
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