Kenrik

1991 300d

130k Miles

I just bought a 1991 300d from an old lady it almost perfect condition... all records showing maintnence up the wazooo she took great care of the car.

Anyway the car runs and drives great but when you hit the gas it leave a GIANT cloud of smoke, enough to cover two lanes and make cars behind you get over.. yeah.. not that great (it does it even when warm) I'm not sure how much of it is due to my lead foot (I dive a G35 Coupe and a Turbocharged 250HP 240sx... this car is for my wife) But I doubt that the car is supposed to smoke this much even if you floor it, I checked the air filter and it looks new so that's not it (I read that if it was cloged it could make it smoke more)

I'm a complete n00b with diesels, I'm used to building sports cars so this is very foregn to me.. So I leave it upto you diesel experts to help me out... PLEASE

Any Ideas? What should I check first?

shdoug

So, in your case Mercedes= My Expensive Race Car Emits Dense Exhaust Smoke.

Too much fuel, late injector timing, or low compression would be my guesses. My experience with diesels is limited to Oldsmobile (Old Ladies Driving Slowly Make Others Be Infuriatingly Late Everyday) but the principles should be the same. I would lean toward the injector pump needing to be rebuilt.

Lorinser880

When was the last tune-up? Previous owner probably didn't drive it hard so it could just be carbon build up in the exhaust system. shdoug also has a point with the injection pump.

ZorroAMG

Don't we need to know what color of smoke before we can suggest anything?

neanderthal

clean the injectors

Kenrik

The Smoke is black... not blue at all (so not oil) and I think I saw a little bit of white smoke but only one time. The car was sitting for maybe 3 weeks before I bought it, how long does it take for diesel fuel to break down?

I put in Lucas diesel fuel additive today, I hope it helps.

Kenrik

Still Smokes, I'm going to check the turbo for shaft play and if it's ok what else can I try without taking it in to a mechanic?

shdoug

Do a cylinder leak-down test. Also, do a search on this forum for others who may have had this problem. I saw something about excessive blow-by somewhere on here.

I can't believe no one commented on my acronyms! That is some funny s**t!

Kenrik

Turbo rebuilt still smokes.. black smoke, WAAAAA help me... Hmm about how much does an injection pump rebuild cost? I don't want to get ripped of because I don't know how much it should be.

bicylindrico

An easy test would be to check boost pressure. Spec. is .85 to .95 bar.

I do agree with Lorinzer880. I would drive very clean old diesels in the past and you could tell the ones that lived the "granny" life never being over 2K RPM's. They would typically only bellow thick smoke for a short time and would seem to clear up after repetitive full throttle runs. If you are getting full boost this car should be running strong. If the performance is so so, there must be an issue. If it runs great without smoke while normal driving, I would consider the fog screen a bonus.

Kenrik

I have done full throttle runs and it did not help. The engine starts perfect and seems to idle/run fine. it smokes (a lot) under anything more then 15% throttle. it seems decent in speed from 0-45 mph if you gas it but anything above that it takes years to gain speed.

When I say smokes a lot... I mean more then a bad running diesel semi... yeah.

Black smoke..

Another thing, I can't seem to hear the turbo spool (freshly rebuilt) IDK if the engine is just to loud to hear it or if maybe the wastegate is stuck open so it's not building boost?

I don't have a boost guage, so I can't tell.. also where would you hook it up on this car?

Sorry I'm a n00b with diesels/benz

I have a turbo 240sx and a Infiniti g35 C so this is a completely different beast for me.

bicylindrico

Any port on the intake manifold will see full boost pressure. You just need a simple pressure guage that will read up to 20 PSI. You can just T in somewhere with some vacuum line. Do you feel a surge in power over say 1500-2000 RPM's? It sounds by your description that boost is likely low. It should have good power from 45 on. The fact the turbo was even touched would lead me to suspect something with the boost pressure. People seem to create problems as often as they fix them.

The boost check is something inexpensive, simple and can be very informative in deciding which direction to take next. You will may even learn a little more about your engine in the process.

myfirstbenz

is your fuel consumption bad? I would just give it an italian tune-up, blow out that soot. If you have maint. records and it is low mileage, I would have a hard time believing anything is worn out.

myfirstbenz

Kudos

Kenrik

I did the italian tune-up, still the same.

Anyway, It was having this issue before I had the turbo rebuilt. That's why I had it rebuilt, because it was smoking I checked the turbo and found it had play, did not spin freely and had oil all in it.

I droped it off at a mercedes diesel specialist to get checked out. I told him not to do any work without my ok I figure if it's anything big I'll just pay the diagnosis fee and fix it myself.

Otherwise i'll just have him fix it.

I only paid $4500 for the car in the first place, if I get this problem sorted out I know the cars worth atleast 8k due to being in perfect condition (paint and interior) and also low miles (for one of these cars) so a few hundreed $$ in fixing it is ok.

Lorinser880

Have your injection pump calibrated and your nozzle tips replaced.

bicylindrico

How about doing some tests first? How about having a reason for spending money and initiating repairs? How about exhausting all simple and inexpensive solutions first prior to rebuilding everything?

Sorry to sound harsh but no one wants to take small steps to end up at a logical solution. This attitude makes a Mercedes Benz an expensive car to own.

bicylindrico

I agree. I doubt the turbo itself needed attention with that mileage but that's no longer an issue. Check that boost!

shdoug

It's a Diesel, what are you going to test? Smoke is either oil burning due to worn rings (not likely since the engine runs on oil and has less than 500,000 miles) or too much fuel. If the engine has good compression, then all that's left is the injection pump and nozzles, right? Pretty straight-forward if you ask me.

bicylindrico

I won't justify this with a response.

shdoug

I will.

Assuming the turbo is spooling and the boost pressure is sufficient, which sounds like it could be the culprit at this point, dude, we're not talking CDI here. It's a mechanical injection pump, right? I've never seen one of these Merc diesels in my life, but are they any different than any other diesels pre-CDI? If they are not a typical scenario then I am talking out my *** and I would appreciate it if you just blow me off rather than insult me.

If it's like every other diesel I've worked on, when the injection pump starts to wear out it throws too much fuel at the engine. I don't know why, they just do. I replaced many of them on other diesel engines and it ALWAYS stopped the smoke and made the engine run like new again. An old-lady-driven diesel engine is not going to have anything mechanically wrong with it unless it ran without oil. Everything inside the engine is coated by heavy oil, or light oil- since diesel is light oil. That's why these engines don't wear out.

So if the turbo is good, what's left? Valve guide seals? Coated by oil, and they generally don't cause smoke under heavy load, only at idle or first start.

Cylinder rings? Seriously, what would it take to wear these out on a Merc? Maybe sitting in a rain forest rusting for 15 years or if someone put windshield washer fluid in the crankcase instead of oil. Short of that, pretty bullet proof.

Ummm, let's see- what else? Too much fuel under acceleration? Sure. Now, what could cause that? Injection pump? Or it could be the injection pump. Then there's always a chance it's the Injection pump.

If it were my car I would run a compression check just to make sure the engine is not a boat anchor. Then I would have the injection pump rebuilt and see if that solves the problem. I would say it's due for a rebuild anyway.

bicylindrico

Look "dude." I was in no way attempting to insult you. After reading your response, I am quite sure I am more familiar with this engine than you. These engines are not "bullet proof" and the do wear out. Just so your aware.

I think Kenrik was looking for some insight as to how to diagnose and possibly repair his car. I am guessing he does not have a diesel compression tester lying around or want to spend several hundred dollars to purchase one. I am guessing he would prefer to not shell out hundreds of dollars to "have the injection pump rebuilt and see if that solves the problem." He would probably want someone to HELP him narrow down the problem with inexpensive tests that he can perform himself. Just so you know, diesel engines do have tests that can be performed to find problems. The injection pump, though crucial to this engine, is not the center of the universe. The turbo is just as critical to the engines performance and drivability. That's why they put one on there.

My purpose for joining this group was honestly to help you guys fix problems. I do have a background with these cars and enjoy helping someone fix their ride with minimal cost. I could puff up my chest like you and try to show everyone why my opinions are gospel. That's not really my style nor do I think it would be appreciated by other members. I promise everyone my opinions will be founded and have some technical merit. Not just guesses unless so stated. I surely hope you don't think you were attempting to show us your technical knowledge with that response. Why again are YOU on this forum?

Lorinser880

No offense taken, sounds like you're not that familiar with diesels. Calibrating the injection pump & at times replacing the nozzle tips is a basic maintenance procedure for all diesel engines, this is like their tune-up, though it's not as often as replacing plugs, filters, etc. of gas engines.

Choice is yours, it's your ride.

bicylindrico

Wish you the best Kenrik. If you decide to do the repairs yourself just let us know and we will do what we can to help you out.

shdoug

Does a non-functioning (locked up or otherwise not creating boost) turbo cause excessive smoking? I've been thinking about that, and I don't see why it would. I could understand a drastic reduction in performance, but smoking?

I don't believe I ever claimed to be an expert. Besides, I've known my share of experts who were wrong at times so experts beware: I'm not always impressed and I don't just believe everything you have to say without question.

I have owned over 50 cars from 7 countries so far in my life and can count on one hand the number of times I have required the assistance of a professional mechanic or friends and family to solve my mechanical problems and still have fingers left over. I have always been proficient at discovering how things are designed to work and allowing them to work that way. That should be worth something. If anyone doesn't like what I have to say then just laugh at me to yourself and move on. It's that easy.