IP, chain stretch or what else could it be?
 

As many of you may have been aware of the trouble that I recently had with my '85 300D turbo, I am wondering what could be the root of the problem. Just a refresher, The car had some injector issues earlier, it was running a little rough and would not really idle on its own when cold and some of the injectors were making sounds like clattering valves. So I changed the old injectors and put in a set of known good injectors that were calibrated to pop at 140 Bar. I thought you could just swap out injectors and that would be that. I was wrong. That's when all the serious problems started. The car ran super rough, it would hardly idle or just sputter out and die, had absolutely no power and smoked horrifically (kind of looked like the car in the MB Autoworks ad at the top of the page but with no smoke from the tires ofcourse). So it was suggested to me that I check my IP timing and to advance it. So I rotated the IP toward the engine block about a 1/4" and the engine ran great. It has lots of power, it idles on its own when cold, idles smoothly otherwise, and the clattering noises are gone. It looks like that did the trick. So now I'm now wondering what was the root of the problem. Is the IP pump worn out, do I have a significant amount of chain stretch or is there something else going on? It doesn't look like the IP timing was ever adjusted as there is a (factory?) scribe mark on the side of the pump were it is attached to the block and it was still lined up before I rotated the pump.

It's good that you have calibrated injectors. One variable gone. If the IP was set at factory spec, corresponding to perfect engine timing, than the IP timing needs to be adjusted for the current engine condition. This is assuming that the valve is properly set.

Yes, the valves are adjusted to specs. Another variable gone?

The timing really should be set, not just moved in a cut and try approach. It's really not too difficult to do with the drip method. All you need is a drip tube or you can easily make one with a junk yard injection feed tube.

Turn the engine to spec (I think 22 BTDC on your) remove the number one injection tube, remove the fitting below and temporarily remove the little cross shaped plunger below the fitting and replace the fitting. Put the drip tube on the fitting and loosen the IP mount nuts. Pump a little hand pump pressure and see if it drips about one drip per second, if not turn the pump to a position where it does. Now put everything back together and don't forget the little cross shaped plunger.

Hope this helps,

sounds to me like you have a stretched chain, hence the timing being retarded. on later models eg om606xxx the ip drive gear has an advance/retard mechanism in it, if yours has this arrangement then it could well be worn slightly. the mechanism works by centrifugal force, so the faster the engine speed the more advance for the injection timing. to be certain as to the correct diagnosis i would recommend you have the chain checked for stretch, there have been numerous posts regarding checking chain stretch.
regards
wagger

Thanks Larry for taking the time to offer me the advice. I value your advice as true gospel. I do have a question about the process. I am assuming that you mean to use the hand priming pump in order to do this. I would probably have to remove the other injection tubes to rotate the pump effectively as it takes brute force to do this otherwise which I managed but my method was truly unorthodox. My guess that the best way to do this is to route the other lines into another container or just let them leak down the side of the block. This may sound crazy but I don't have a problem with letting them leak down the side of the block as there is a lot of greasy grime down there and the leaking fuel would help clean it up a little.

Wagger, I have no idea if my IP has the arrangement you are talking about. I haven't come across any literature that goes into any real detail about the IP. My CD shop manual doesn't even go into too much detail about it.
I have read the various threads regarding the timing chain in the past but I haven't tried any of them yet. Even if I were to have a stretched chain at this point, I don't have the time nor the ambition to replace it myself. I have many reservations about attempting it on my own as with my luck I would end up with a disaster on my hands. I have spoken to an independent MB shop about replacing the chain and it would cost me more money than I could really afford to spend.

No, when I talked about the operating the pump, I meant the hand pump. Once the engine is in the correct position, you will operate the hand pump and turn the IP just enough get the right drip. Don't forget to loosen the nuts.

Once the timing is set as I describe, then you will know where you're at. If it still does not run as it should then as wagger recommends you will need to check for chain stretch and advance mechanism in that order.

If it is a higher mileage engine that has not had frequent oil changese, you may very well have chain stretch.

Good luck,

Larry, I'm a little confused as to what you mean by the hand pump. The only pump I'm aware of on the IP is the priming pump. I haven't tried your suggestion yet. The first time I tried adjusting the pump, it wouldn't budge, but I thought there were only two nuts. Then I found the third one under the pump and it was movable but the injector lines made it tough to rotate without removing them, but not impossible. So yes, I understand the importance of loosening all of the nuts.
My car with 223K miles has a solid history of 3K mile oil changes.
One question, let's say I do this to try to get the right drip, it doesn't happen or I do get the right drip but then the engine ends up running bad like before, what then? Sorry to pick your brain but I want to be thorough as possible.

Have you checked chain stretch?

Compressoin check? How are cold starts?

Air leaking into the fuel system, even from little pin pricks here and there, can cause trouble.

There generaly arent that many things that will make a diesel run bad. It can't be too hard to find.

Absolute worst case is the injection pump being bad or some buggered up valve/seats I'd imagine.(i know you really want to hear that)

I didn't think about checking the chain stretch the last time I adjusted the valves. It wasn't something I was aware of at the time. The car hasn't had a compression check in almost 7 years. It had about 170K miles on it. The numbers from the record were 380,380,380,340,295. They don't sound too even. I'll find out how it starts tomorrow as I haven't had to go anywhere since I did the IP adjustment.
I think I'm over hearing the worst things by now.

Since moving the pump to advance it cured your problem I would be very curious to see how stretched the chain is. Checking the chain stretch is very easy and setting the timing before checking the stretch seems like putting the cart before the horse since if a new chain was required then the timing likely would need to be reset again. Spend and hour, pull the valve cover, check the stretch, might as well check and adjust the valves if neccessary while you are there, and if needed roll in a new chain. RT

RT, I've read many of the threads about checking chain stretch, and yes it is very easy. I plan on pulling the valve cover during spring break a week from now and readjusting the valves at the same time. I'm not ambitious enough to attempt to roll in another chain if the chain were stretched significantly. I'm afraid to have a disaster on my hands should something go wrong, which in my case would more than likely happen. I would prefer to have someone else do it but the prices I've been quoted are prohibitive.

Satus Update
 

I drove the car Sunday and it started fine cold and idled on its own for the first time since I have owned the car. The idle was not too smooth though but I guess no diesel idles perfectly when its first started cold. Also when driving off, the engine sounded like it had marbles rolling around in the combustion chambers maybe not unlike the sound of preignition in a gasser. The engine seems to sound a bit louder as well. I think it may be a little too advanced right now but it seems to have enough power while driving and it did not run any hotter than it usually does. It may take a little tinkering to get it right.
As far a new chain goes, I'm not going to mess with the old one. I plan on leaving the chain as it is for now.
By the responses I have so far received, I am sure there is some amount of chain stretch of which I'll only be able to find out when I pull the valve cover.
I'm curious how much is too much?

DJ,

Idle should be fairly smooth, may be a little too advanced OR still a little retarded. Try moving again one way or the other and see what happens.

As far as the chain stretch , some say 4 degrees is enough to change, most say around 7 degrees is change time. I'd say if it's at 4, tweak the IP till it runs well and forget about it. As long as you change oil often or use synth oil, you'll be fine for MANY k miles!

Tom, I'm thinking at this point that it might be a little too advanced because of what sounds kind of like what pinging or pre-ignition would be in a diesel, if there is such a thing. I wish rotating the IP would be as easy as rotating a distributor on a gasser. That way I could adjust it while the engine was running. I'll have to just try and see what setting will make it run best.
I thought that since the car has had a solid history of 3K mile oil changes, (Everyone: please, no oil discussions here:eek: ) it shouldn't have much chain stretch.