Bought my '87 in 2005 and it's spent more time sitting than running due to a string of events that don't really matter that much here. Short version is the car has been sitting still since the end of 2008. When I tried to start it a few months ago, it would crank but never start. A friend helped me with it one evening and made an adjustment on top of the injection pump that got it running. I'm not clear on exactly what was done and am hoping to stare at it again tonight or tomorrow to make more sense of what we changed that night. In any case, it will now start instantly and has no problem maintaining a smooth idle. However, as soon as the accelerator is pressed the car emits lots of diesel smoke and will not spin up past about 1500rpm.

Before the car was parked, I blocked off the EGR using a kit sold by somebody on the forum (Brian Carleton, as I recall?). Several of the vacuum lines appear to have been disconnected and I'm going to try to chase them down using the diagram posted in the forums. I've tried running a can of diesel purge through and it didn't run any better on that than on pump diesel. There is a slight whine coming from somewhere in the engine compartment that I haven't been able to identify. I'd love to get some help with basic troubleshooting. All my experience is on wrenching with gas cars and motorcycles so I'm reasonably handy in the garage but a bit out of my element here. My gut here is that the turbocharger isn't spooling, but I might be totally off base.

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1987 Mercedes 300D

You say your getting a lot of "Diesel Smoke" at 1500 RPM's - Is the smoke Black - or Gray ?
I don't own a 124 but it is very close to my SDL in engine design.
My understanding is - though I have not experienced the exact same problem - Black smoke = unburned fuel.
Have you checked your intake from the filter all the way up to the crossover pipe for a blockage?

It sounds to me that the engine may be starving for air at RPM's above idle if the smoke is Black and you can't get above 1500 RPM.
Also, the adjustment made to the IP may have been to the ALDA. I don't know of anything else that is adjustable on top of the IP. This could be a bad thing to have adjusted without knowing what was done.

Have you checked your fuel filters or replaced them? Fuel starvation can limit RPM's .

How old is your fuel and is it clean?

I had a similar issue when I bought MY SDL , where it had been sitting for 2-3 years. Until I actually drove it and "stomped" on it several times I had no power. After getting on the accelerator and driving at moderate RPM's I did see some improvement - I don't recall what my conclusion was - but sitting caused the engine to not perform well.
Of course there were a number of real problems that needed to be addressed.

Really need more info. There are many issues that can cause this problem including the IP.

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1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
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first exhaust port has a brass plug. pull it out. try to run that way. IT WILL BE LOUD!
if it works sorta ok or at least shows an improvement, then your cat is plugged. if you have still got a giant football ontop of your turbo, then your trapOX could be plugged... it's a factory recall, and MB will replace it for free.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
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My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

It's definitely unburned fuel (black smoke). I'll take a look all the way through the intake track and verify that it's clear. Agreed that it sounds like it's starving for air for some reason.

The ALDA was removed several years ago (sorry, forgot to mention that in the OP). The car has been run since then with no problems. To the best of my recollection I've replaced both fuel filters in the time I've owned the car and less than 10k miles has been put on it. Also, given the black smoke I'm hesitant to suspect a fuel starvation problem. The fuel in the tank is old, but I've also tried routing the fuel inlet and return lines directly into a can of fresh diesel fuel and it didn't improve the symptoms.

The trap oxidizer was replaced before I got the car. Hope these answers help a bit. Thanks for the suggestions.

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1987 Mercedes 300D

Vstech mentioned in his post the possibility of an exhaust restriction - this may as well be an issue where you are getting sufficient intake flow but the catalyst is blocked.
I have read in posts here that the darn catalysts can become clogged pretty quickly - some have tested this by opening the pipe plug port on the exhaust manifold as Vstech has suggested. This is usually a no start issue that can't be fixed until there is sufficient air flow through the system.
The black smoke you see may also be partially soot from deposits in the cat , manifold or turbo.
So you may have a number of problems - possibly partially clogged catalyst and/ or intake.
On the intake box there is a flapper or valve that pivots - you might check this.
I have also read that some have had birds nests and rats nests in the intake.
One problem that occurs with catalyst is that large flakes of soot in the exhaust manifold and turbo fall off and block the ports in the catalyst.
If this is the problem then removing the plug in the exhaust manifold should prove this out.
If the catalyst is damaged , it should be covered under warranty - I think - since it is an emission item - though I have heard ther is a limited warranty on this.
It is bypassable (is that a word) for testing.: ).....

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1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

Thanks again. I'll check the intake track as well as removing the pipe plug to check the exhaust side. As to the black smoke being from deposits, I suppose that's possible but it's directly proportional to the accelerator input rather than a constant amount.

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1987 Mercedes 300D

Probably not the turbo if it won't rev up while in Park.

As stated above, it may be the exhaust is plugged up. When I was having similar issues, I cut off the 1st oxidizer/Cat completely to test it, but still didn't work. I cut it open just for kicks and it was 50% clogged, but good enough to run okay

Mine ended up being bad/clogged injectors and a Bad IP, but I had starting issues too. Flutter the gas pedal and see if you can get th rpms up. Once mine was running it still performed bad until the engine was driven a while, synthetic oil, and an Italian tune-up!

Take out the air filter for now and put a long screw driver in the mass air flow unit to be sure the flap is open and air is getting in.

Could be a vacuum thing..... Make sure the banjo bolt (vacuum fitting) on the driver side of the intake manifold is clear of soot as well as that line to the overboost controllers on drivers side inner fender wall.

let us know

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1987 300TD 147,000 miles- Palomino leather interior, 1995 facelift and body cladding, E350 wheels, Rebuilt suspension and sport springs, rebuilt turbo, New Monarch injection pump and injectors....and the list goes on and on...

Mouse/rat/squirrel nest in the inlet for the air filter housing? Try running him with the cover off the filter housing.

Jay.

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On the road, currently:
'83 300D (German spec.) 168k mi. - - Wolfgang (tucked snugly away for the winter!)
'87 300D 375k mi. - finally went over to "The Dark Side"
'87 300TD 225k mi.
Cannondale 66cm CAAD5 w/Campy/Jamis Aurora
Hujsak Custom Fixie/Landshark Track Shark Custom/Ahearne Custom 29'er

When was the last time the car ran properly? I had loss of power and laggy acceleration at high rpms but KNEW it couldn't be my fuel filter...sure enough, it was! It is cheap and may be the issue. Can you give us more info as to when it went from working to not working? Also why the "adjustment" was made to the IP?

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

The last time the car was driven regularly was probably 2006 or early 2007. I was driving through town and the front suspension failed (as I recall, a ball joint separated on the passenger side). After that was repaired, the car ended up parked for a while as I dealt with some other projects. Deployed to Iraq in '07 and the car stayed in the driveway until I got back in '08. Somewhere around October of 2008 I got it started and drove it a couple of times as I made a list of the things it would need to go back on the road full time. It sat for a couple of weeks at one point and I was unable to get it back started when I returned to it. It would crank and the engine would shake and briefly accelerate like it was about to start, then it would go back to normal cranking speed.

From there, the car sat until last summer when a friend who works on diesel trucks regularly stopped by and helped me take another look at it. Wish I had a picture of the top of the IP handy, but what we adjusted was a castellated nut that seemed to have become loose. Once it was tightened back down the car started immediately. It still had no power off idle. At the time I was hoping to get the car inspected and back on the road, but started school part time (while working full time) just a few weeks later and neglected the car one more time.

At this point I just want to get the car running well enough to get an inspection, then clean it up and sell it to someone that will actually use it. It's a great car, and a huge shame that I've let it sit for several years now neglected. Has less than 190k miles on it and somebody else will get a lot of good years out of it once it's sorted back out again.

Didn't get a chance to fool with it last night, but tonight should be better. Thanks again for all the suggestions.

__________________
1987 Mercedes 300D

Beware diesel rodents!
Beware diesel rodents!






.

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I still vote filters. And while it is supposed to be a self bleeding system, I've never had such luck, so once you change filter crack the banjo bolt right above it and then crank.

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000

I'm not following your logic. How would a fuel filter explain an apparent overfueling issue? I'm getting black smoke proportional to 'throttle' input and no problem starting.

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1987 Mercedes 300D

I agree that black smoke proportional to increase in throttle seems to be
an incomplete burning of fuel and lack of air.
You might consider IP timing and injectors as well as intake issues.
If your IP timing is late you are going to be producing a lot of black smoke.
If you have a couple of injectors popping at the wrong time - this could add to the problem.
I would first check the entire intake circuit for problems.
Pull the tube that runs from the filter to the turbo input and the crossover pipe
to be sure nothing is blocking the air path.
Also check the "flapper" - the element in the filter housing that acts
as a mass air flow sensor for free movement.
Some more things to consider.

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

Great talking with you.
VIN# would help this diagnosis.
Hope to see pictures of the EGR/transducer/vacuum system soon.

A few things we discussed to check:

* Vacuum hose/line damage.
* Wire damage (rodent).
* Plugged air filter (rodent).
* Intake air flow sensor flap failing to react/move.

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