If you have the Rack Dampner/Governor Idle Pin you have an MW Fuel Injectin Pump and don't have delivery valve seals (O-rings). You only have the copper Crush Washers.

Stuck rings. Marvel Mystery Oil cleared it up. No nailing now and it also starts in cold temps that it wouldn't have before.

Sorry, not an MB star-branded solution.:whip:

-Rog

The oil shifts the ignition point towards late and extends the burn curve which mostly results in less noise.

Your new timing chain advances the timing if the pump has stayed at the same mark.

Using higher cetane fuel eliminates the problem. That points to too early timing.
Having a short look at data sheets the ULSD Diesel has a very low cetane of only 40-43. That in combination with early timing tends to knock as the moment of ignition is less defined.

Also the noise disappears with full or half throttle. That also points to too early timing.

Might be only 2-3 degrees early. So if you turn the IP all the way away from the engine block that should make a noticable difference.

The adjusting range of the pump is 10degrees so you maybe have to turn the pump only half away from the engine block.

When was your last italian tune up?


Gruß
Volker

Ok, I checked the IP timing this morning using this method (below), as I don't have a drip tube yet. I did it three times in a row, using two sets of hands and eyes, and came up with right around 17-18 degrees BTDC. According to this site, using this method I should see 24. This isn't as accurate as the drip method I'm sure, but at this point it would be safe to say that I should advance the pump a bit and see the results? Weird, given the symptoms I was beginning to be sure I'd find it too far advanced after reading what Volker posted that all makes sense...

Injection Pump Timing Adjustment for Mercedes 617 Engines - Topic

Well, o-rings and delivery valves seals are different things. I know that the earlier OM617 engines did not use o-rings, but did they also have a delivery valve with no copper sealing ring inside?

I don't like that method, it just doesn't read right to me. As I understand it, fuel "just welling up" in the chamber means that the piston has retracted down far enough to expose the opening that allows fuel to enter. I don't think that is the same as "start of delivery".

If you don't have the fancy drip tube, you can use the bubble method instead, which simply replaces the fuel drip with air, and use the #1 injection line instead of the drip tube. You do need a source of air (lungs can do this, or low air pressure from a compressor) and a jar to immerse the end of the injection line. Use the same steps in the factory manual, but instead of watching for the drip, you watch for bubbles to go from a stream to a much smaller stream.

Ok, looking in the FSM for the OM617a, procedure 07.1-210, no o-ring but there is a copper washer. When that copper washer leaks, it can cause a rough idle. Copper washers are supposed to be replaced with new every time the delivery valve is opened up. They are cheap, but the injection pump and lines need to be clean clean clean before all the injection lines are loosened up and removed and the delivery valves removed in order to ensure that no dirt / grit / lint or other contaminant gets into an injector and clogs or damages a nozzle.

It would be internal and not visible around the top of the IP. If you idle is smooth, this is probably not your problem. If one or more copper seals are leaking, they allow some fuel to leak off and less fuel is delivered to the affected injector(s) compared to the others. This is most noticeable at idle.

Given this, and that you've already removed / replaced the #1 delivery valve and you may not have replaced the copper seal with new, I'd recommend you order at least a complete set and maybe some extras if you plan to adjust timing in the future, and "rebuild" all the delivery valves with new washers. New springs are recommended by the FSM as well, but most people don't bother.

I would imagine that old weak springs would allow an earlier release of fuel from the DV, but the injector pressure setting would hold that build up of pressure until the set point is reached, so maybe no effect?

I've not removed any delivery valves. I do intend to look into the washer and seals, thank you guys for that.

There is definitely something off here. The injection pump is already at its far max retard position, despite the scratch marks lining up. It cannot be tilted farther from the engine. I guess I won't know for sure until I do a proper timing check.

The method in the link you posted requires that the #1 delivery valve be removed. I think you should return the injection pump timing to the original marked position and forget about that approach. Injection pump timing needs only be checked when the injection pump is removed / installed, and then once again after a few thousand miles to make sure it hasn't moved. After that it typically never needs to be adjusted again in the life of the car.

Well against my better judgement and the advice of all haha, I advanced the IP slightly (see attachment) and WOW. It's 30 degrees out and there wasn't a hint of nailing when driving. The idle is silky smooth both in lack of vibration and lack of lope. The idle noise (hot or cold) seems be slightly louder and more "diesely" but that dissappears as soon as the engine revs above idle.
I may try to move the pump back slight more towards the mark but assuming I didn't move it too much, I'd be very happy with how it's running now.

That looks like a very small adjustment in IP timing, I'm surprised that it would have any effect at all!

Bottom line, it worked! Congrats!

What I can see on the picture I would guess your pump was advanced about 5 degrees earlier.
According to the facts until now I would not have expected that behavior, but your description seems like the engine runs normal now.

Keep in mind that the fuel you use is not the same fuel the engine was designed for timing wise. As a Diesel engine is always an adaption to ignition delay you can leave the timing the way it is now if it runs fine.


Gruß
Volker