My car smokes really bad under hard boost, more than it ever has before. Can anybody tell me what the problem might be. Thanks.

I think the Injection Pump Timing is off a little bit. Did this happen all of a sudden or has it been getting worse over time?

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The problem started quite suddenly and was fairly bad when it started, although with the progression of time the problem seems to be compounding. The dealer said it was just some small problem that would clear itself up, but it never has. The dealer made the diagnosis about 2 years ago. They also assured me that the car will not be damaged if run in its present condition. I would think that the dealer is incorrect, and since I have been driving for some time I am hoping that I have not created more problems, or protracted the life of the engine in any way. I am a fairly good mechanic, however I have never worked on a diesel engine before. How do I go about fixing the problem? Thank you for your response.

Its probaby not going to cause anymore problems, the engine is just not going to run correctly. If you need to adjust the injection pump, some special tools are needed, and you need to use what is called the Drip Method, set the engine at 15 degrees before top dead center on #1 and hook up a line to cylinder on fuel line and watch it drip, it should drip once every 15 seconds. There is another way to adjust it, I forget what it is off hand, maybe someone else on the board could help you with that.

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Tools needed for injection pump timing

The procedure requires only a few do-it-yourself tools at Craftsman quality or above (we'll set the "floor" level on tools for do-it-yourselfer where Craftsman equals the minimum quality needed).
Floor jack and stands
27 mm socket and long ratchet or breaker-length bar
Heavy duty prybar
8 mm 1/4" drive socket with ratchet and long extension
8 mm closed end wrench
17 mm wrench
13 mm combination wrench (See #13 below which provides an excellent tool for this particular procedure)
Small block of wood
High quality paper towels (Bounty or above)
An extra set of eyes to watch the #1 injection valve to determine timing
Your 1/2" drive ratcheting torque wrench will make an excellent long
ratchet for this job
If you have an Ace Hardware Store in your area, by all means buy a 13 mm Ace Professional Gear Wrench combination ratchet. This tool is open-ended at one end and has a "ratcheting" (literally) box end at the other end. It is a very well-made tool, yet it is also very slim, particularly on the box end. Smooth, high quality finish.
Instructions

Assume cold engine
Remove the #1 injection line. [Don't take anything off of the injection pump except the injector pipe. If you even __think__ of removing anything else (e.g., the nuts that hold the valves to the top of the pump body), you will regret it!]
Jack up the front end and block it.
Pump the hand pump several times to build pressure.
With 27 mm socket and bar, turn the engine over at the crankshaft until you have gone through a compression stroke on #1 -- this will be noted by fuel coming out of the #1 open valve.
Roll the corner of a paper towel into a pointed end.
Twist and insert this into the #1 injection valve and remove all fuel.
Note that you'll have to repeat this 2 - 3 times to get all fuel out.
Turn the engine over by hand until you go through the exhaust stroke.
Turn the engine until you get within 40 degrees of TDC (TDC = stub on crankshaft pulley).
With your helper watching the injection valve closely, turn the crank as slow as possible by hand until the point where your helper first notices fuel "welling up" in the bottom of the injection valve. [It will be beneficial at this point to mark the "bottom" side of the pulley with chalk to inform you, underneath the car, that you are getting near the mark.
Note the degree of advance at the timing marks on the crankshaft pulley. The correct timing should be BTDC 24 degrees +/- 1 degree.
Advance is accomplished by swiveling the injection pump toward the engine at the top. Retard is the reverse.
If your timing is within one degree of 24 degrees, you are finished. If not, continue.
Pregnant pause. Still with me? -- then go to the next step.
If your timing is not within specs, you must first loosen the nuts that hold the injection pump in place. There are four, and three can be accessed topside.
Three of the nuts attach the IP to the engine toward the front (two topside and one below) and one is attached to a bracket at the rear (accessible topside). The Gear Wrench greatly, greatly simplifies loosening the pump.
The factory workshop manual illustrates the need to "bend" a 13 mm boxed end wrench 45 degrees to the left for use in adjusting the timing. You do not need to do this with the Gear Wrench. [Please note that this tool is not a toy, by the way.]
There are two ways to adjust the pump:
the Jeweler's method and
the Neanderthal method
Both methods yield equally good results, both have their own inherent levels of risk, but they each require significantly different amounts of time. I prefer the Neanderthal method because my risk/benefit analysis suggests that this method is less risky to me, yet more fun. I will thus describe the Neanderthal method and, in parentheses (e.g., [ ]), will describe the Jeweler's method, where applicable.

After loosening the four "holding" nuts, loosen (but do not remove) the remaining anti-vibration interconnections between the pipes. [Jeweler's method: remove all remaining injection pump lines.]
Using your judiciously-placed prybar, advance by pushing toward the engine with the injection pump. If advancing is not applicable to your timing, push from between engine and injection pump to retard. For advancing on the 123 chassis (300D), the area immediately under the steering adjusting bolt provided an excellent "prybase", with contact on the injection pump provided by the small block of wood. Please be certain that you do not put pressure on the ALDA unit on the top of the injection pump. If unsure what is meant by the ALDA unit, re-read paragraph on assumptions and discontinue process. [Jeweler's method: Same procedure, but less force is needed because of all lines removed.]
Please note that the movement of the injection pump with Neanderthal method is more difficult than Jeweler's method, since 4 of the lines are still attached. Why this method then, you might ask? Later, please. When moving the pump, it will seem as if the injection pump is not moving, but it is. The remaining lines are very stout and will be "springy" while adjusting -- look at them while adjusting, you'll see. Therefore, you need to hold the tension with the prybar and have someone tighten one of the front three mounting nuts for you to hold the new adjustment in place.
Recheck the timing, by first repeating steps 4 - 9. Readjust if necessary.
When the timing is complete, bend the #1 pipe so that the pipe attaches to the injector valve and injector with no force-fitting. It is critical that the line's nuts do not get cross-threaded. [Jeweler's method: rebend all remaining injection pump lines.)
Reattach the anti-vibration interconnections. Be careful to not overtighten them. You have now successfully completed injection pump timing for the 617 engine.

Contrasting the Neanderthal versus Jeweler's Method

Neanderthal

Positives

Quicker, more macho, more fun, much less danger of cross-threading. Injection pipes will "set" in new found position over time.

Negatives

Harder to move injection pump (4 lines remain). Potential threat of damaging injection pump (very minimal if prudent).

Jeweler's

Positive

Easier to move pump (all lines are removed), Injection pipes are already "set" when manually bent.

Negatives

Higher probability of cross-threading injection lines, less fun, messier (you have all 5 lines off spilling diesel fuel).

http://hsb.baylor.edu/html/easley/mercedes/welcome.htm

I saw some reduction in turbo-boost smoke with a clean new air filter. It was surprising how much stuff was trapped in the old one. Also, if your EGR valve has not been disabled, your intake manifold may be caked up with soot to the extent of reducing air flow. Less air, more smoke.

Ken300D
1982 300D
1987 300D (subject of this discussion)

1987 Model would not have a 617 engine. IP timing is different on a 603.

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Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

Tuner and Timer, interesting suggestion and great write-up (are you the author or are you passing it along? because it does look familiar!)! SDL, Unfortunately it does not apply to your car or engine! For OM603.961 engine info search for commentary from psfred or gsxr, both these individuals have both knowledge and experience with respect to these six cylinder engines.

You would be well advised to obtain the relevant technical info i.e. the MB engine manual or the CD which inclues this manual before delving into the intricate and precise fuel injection systems. You will at the very least need to know the torque specs for any parts you remove, replace or adjust.

As an aside before you jump into IP timing play have you checked and eliminated the simpler possible problems like EGR, Air recirculation, turbo bearing seal leakage. The question that might be asked is how would the timing have changed enough over a short period to produce the apparent effect? The timing chain is unlikely to strech so much so quickly? the IP should not have rotated out of position easily? Have your injectors been "Lubro Moly Diesel Purged" lately, fuel and air filters changed out? How's your crankcase oil consumption, i. e. is the smoking the product of incomplete combustion or exhaust fouling?

I own the same car so I'll be watching to see how you resolve your problem and what the final diagnosis/problem is, Good Luck!