Mine idles fine. Its just when its cold it makes that random knocking noise.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

I remember hearing someone mention that the chain could be stretch, and injector pop pressure could be out of spec to the point where it's affecting timing significantly and causing knocking/pinging...is this possible?

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

Did you take a stethoscope and narrow down where it is coming from?

If I had to guess, to me it sounds like a flex plate issue.


.

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1983 123.133 California
- GreaseCar Veg System

My '83 was making quite a racket and I found the alternator to be loose. Not to the point you could see it jumping, but just applying hand pressure to the top off the alternator (while running) identified the problem. My noise wasn't identical to yours, but it's a quick check.

Good luck.

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-RK
'83 240D, auto, 170,000 miles "Old Blue"
'87 300TD, 140,000 miles

My 616 did the same thing. It was the No 1 cylinder as well. I found that the Delivery Valve was bad. The seat had an eroded spot on it and it would not seal properly.

After replacing the Delivery Valve and spring, all is good.

I'm assuming the delivery valve is located inside of the IP? How hard is that to replace?

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

It is on top of the IP. You have to remove the injector line first. The Delivery Valve is located under the fitting on top of the IP that the injector line screwed on to, the fitting is called the Delivery Valve Holder.

To remove the Delivery Valve Holder, it unscrews from the Barrel on the top of the IP. It has a hex on its out side, 15mm I think. What ever you do do not touch the two 13mm nuts that are on either side of the Delivery Valve Holder, as those nuts hold the Barrel in place.

Be very careful to clean the the top of the IP as when the Delivery Valve Holder is removed, the Barrel and Plunger will be exposed, and dirt is a killer.

When the DV holder is removed, there is a small spring under it, it may stick in the DV holder and then drop out. DO NOT LOOSE IT. Then you will be looking at the top of the DV, there should be a coper washer underneath the Delivery Valve. Inspect the seat of the DV for damage, erosion, or any excessive wear.

I am not at home right now so if anyone can chime in with a better description please do.