Need Help Tons of Black Smoke 91 300d
 

Ok so I have a 1991 300d 2.5l turbo diesel.

Perfect condition inside and out, florida car no rust. 130k Miles full records of all maintnence for the past 16 years.. I got it from a nice old lady for a good deal :) hehehe.

Anyway I have been having an issue with BLACK smoke from day one.
it smokes a little bit of black smoke at idle and once you get over 15% throttle it gets really bad.. like.. leave a smoke screen all cars behind you get over and give you the finger bad...Like old semi truck bad... (leaves a cloud huge that hangs in the air if you punch it) I had the turbo rebuilt (the turbo had blown seals and I figgured rebuilding it would fix this problem) But it's still doing it, I don't hear the turbo spool but I don't know if it's because the engine is just to loud or if maybe the wastegate is stuck open (no boost?) I need to get this thing fixed and IDK what to do.

Maybe an injection issue?

I hear a little bit of (I guess the term is) "nailing" at idel when it's cold. just a few clanking sounds ever few seconds.

Any ideas?
Also anyone know a good mechanic in the Miami/Fort Lauderdale area?

BTW it's for sale if anyone is interested.

More Info: IDK how the car is supposed to feel because it has had this problem since I got it but it seems pretty peppey from 0-45mph when it's shifting gears (And reving to around 3-3.5 k) but it pours out black smoke.
Top end Sucks... 50 - 80mph in what feels years...

sure sounds like lack of boost to me.
black smoke is too much fuel in the combustion, so lack of air would equate to black smoke too.
whatcha asking for it?
John

Let's start with the basics. Black smoke is caused by not enough air for the amount of fuel being injected. Timing can have an affect on smoke but not to the degree as you descibe it.

Start with the air intake. Make sure there are no obstructions. A severly oil soaked paper filter can cause problems. I have seen cars where the intake hose from the filter to the turbo will collapse because of age and a clogged filter. (I am not familiar with the intake on a 1991 to know if that could exist on your car.) Look to see if the last mechanic forgot to remove a rag from the intake. These are the inexpensive possibilities.

The expensive options have to do with the injection pump. This is not as likely but not impossible. For example some diesels need to have the injection pump adjusted and the timing adjusted when taking the car to high elevations.

TimK

The black smoke kinda means you are not fully burning the fuel being injected. Combine that with the poor power, the first thing that comes to mind is poor compression. So, you'd want to run or have somebody run a compression test on the car.

It could be the rings are messed up because the little old lady drove it slowly around town. Or it could be the engine is worn out due to poor maintenance (i.e. oil changes). Do the records show lots of oil changes?

You could also have severe airway obstruction due to a clogged air filter. So be sure to check that out and maybe just replace it.

Ken300D

I have records for oil changes every 2500 miles, All different types of maintnence, the old lady even kept a mileage log. According to the title she only drove 30k miles in the past 10 years.. which seems about right because she is 90 and only drove it to church and the store. :) BTW she is the original owner. it has a new airfilter and the intake is not clogged.

The engine is clean... very clean for a car of this age and cold starts are perfect (better then my G35 Coupe)

I don't hear it building any boost. So what should I check out with the turbo? I just had it rebuilt and the guy said it was in good condition except for the seals being blown. Maybe something with the wastegate?? where should I start first?

What's making me not think turbo is the fact that it smokes a bit at idle... and that would have nothing to do with the turbo right?

Maybe the injection pump timing is off?

You just do not have enough air /oxygen to combust the fuel probably. Read the boost from your turbo with a gauge extended into the cab. Check the archives. Save more complicated things for later. It has to be a given you are not experiencing this because of a dirty oil soaked air filter.
Unless you have real problems as you rebuilt the turbo not long ago. You would have noticed that. A restricted exhaust could do it as well by not allowing enough air into the engine. That would make the car quite slow as well..
Is there a bolt you remove on the manifold to get an indication on this model? If that exists you just measure the exhaust pressure in the exhaust manifold. Maximum 30 lbs pressure comes to mind but I would like to see less. The specs are posted somewhere. Or just drop the header pipe a little. This problem should rectify with a little work you can do yourself to locate the problem.

Clean the banjo bolt that is on the intake manifold toward the drivers side.

If that doesn't work then try manually opening the turbo wastegate with a hand vaccuum pump to see if you get boost. If so then take a look at the vaccuum modulators and look for leaks.

Also, you might want to replace the spin-on fuel filter and also the main tank filter screen.

All sounds like real good advice. And I'll throw one more possibility into the ring. It seems to me that a stuck EGR valve will cause huge clouds of smoke--black I think, because a stuck open EGR will release boost. I'm most familiar with the 123, so does anyone know if the 91 has a similar EGR setup?

Ahh a little old laddy diesel, that thing is probably sooted up. I bet the overboost solinoid(sp?) is plugged up. You will see some vacuum lines coming out of the intake manifold, remove those if they are full of tar clean them.


The problem with this car is that it hasn't been driven, you need to drive it. Short trips, low rpm, and light use kill diesels. If it were my car I'd remove and clean out the intake, kill the EGR, have the injectors tested, then run the living hell out of it. Find a good steep hill, put your foot down and hold it their, you want to bounce it off the IP limiter which should be about 5k rpm. That should blow a bunch of crap out.

It sounds like its not building boost but adding fuel.

After its running better take it on a long highway trip.

Ken, I don't completely agree with you. Even though black smoke means the fuel is not being fully burned, it is caused by the lack of oxygen. White smoke is caused by low compression when there is not enough heat to cause all of the fuel to be ignited and react with the oxygen.

TimK