Another Black Smoke Question???? - PeachParts Mercedes-Benz Forum

Army-Ant · #1 08-22-2007, 12:09 AM

Ive done my research on the forum....there are lot of opinions out there as to causes or reasons for black smoke....there are also a lot of threads. BUT theres not a thread that matches my problem or vehicle.
Ive had my car (1976 240D W115, 4 cylinder, auto.) for a few weeks now...Ive done all the usual "this is my first MB diesel" stuff...replaced glow plugs, both fuel filters, oil, oil filter, all the belts and cleaned the air filter element (and added some fresh oil to the bath). About 6 days ago I added some STP diesel fuel cleaner/additive when I put in about 8 gall. of fuel. Today I noticed, after filling up, a lot of black smoke at start up, idle and acceleration. Theres alot of black soot around the trunk and bumper area whereas before I DIDN'T have this problem....a little white smoke at start up...some smoke on hard acceleration (couldnt tell what color). It starts religiously on the 2nd attempt ( 1st if its warmed up), idles steadily, decent pick-up for '76 diesel and quick abrupt shut off. Ive got people driving around me and giving me weird stares and NOT because my car is yellow. Its embarrassing.
Where should I start? I'd like to do as much of this myself so that I can familiarize myself with the car and appreciate it more. Im not schooled with diesels so PLEASE dont feel like you'd be over-explaining anything...the more detailed the better.
Thank you.

kerry · #2 08-22-2007, 12:35 AM

Black smoke is unburned fuel. You're either getting too much fuel or not enough air. It'd check the air end first. Remove the air cleaner and run it for a short time. Does it still have black smoke?

Army-Ant · #3 08-22-2007, 12:51 AM

Just so Im not confused...when you say "air cleaner"...you mean the metal thing that I referred to as the "air filter element" thats located in the oil bath? Do I let it idle w/o it or drive the car around w/o it? I wont be able to till tomorrow....
Lets say it still smokes....what then?
Lets say it doesnt smoke...what then?

Army-Ant · #4 08-22-2007, 09:39 AM

I could really use the help here. If someone could just break down the elimination process I would appreciate it. Then I'll delete this thread.

rrgrassi · #5 08-22-2007, 09:49 AM

No need to delete the thread. It will help someone else down the line.

Remove the air filter element. Sometimes an oil bath can restrict air flow until the oil becomes a film on the filter element. Also make sure all air passages from the beginning all the way to the intake are free from obstruction. Does this car have an EGR? Check the intake for exessive carbon buildup. This will restrict air flow as well.

Have you done a valve adjustment yet? valves that are too tight do not close fully, resulting in incomplete combustion.

Our new TDI has no problem belching black smoke under WOT. Also every TDI that I have seen has the sooty bumper. Funny how my MB does not, and it has no problem sending a nice grey fog at WOT either.

kerry · #6 08-22-2007, 10:01 AM

In your tests, you're going to have to repeat the conditions under which the smoke is occuring. I'm putting my money on an air restriction of some kind. Black smoke is soot so the excessive fuel has combusted, but not cleanly. I think if therre was a compression problem, the fuel would not be burning and would be showing up as grey smoke. Same with tight valves.
It's been many years since I messed with an oil bath air filter, but is it possible there is too much oil in it?
No EGR on a 76 (I think).
I would disconnect the whole oil bath filter assembly from the intake, look inside the intake and then take a brief test drive with an open intake manifold.

Army-Ant · #7 08-22-2007, 10:23 AM

"Remove the air filter element."
Do I remove it permanently? Or just clean it w/ diesel fuel and replace? How crucial is it that the oil in the bath be the same grade that I used in the oil change? Cuz its not the same. Rotella 15W 40 oil change...Sae 30 in the oil bath.

Does this car have an EGR?
I dont know. What does it look like and where exactly would it be? If it does, how do I clean the carbon build up?

Have you done a valve adjustment yet?
No I havent. Ive read that some people do it themselves and others say take em to a shop. I feel like I would like to learn to DIY this so that I can service my own car, BUT I dont want to screw it up either. This is a daily driver.

Also every TDI that I have seen has the sooty bumper.
The problem is...as of a day ago...I never had a sooty bumper. Did I get bad fuel?? I read that I should be buying my fuel at truck stops rather than Wally World. I also added "STOP LEAK" when I changed my oil...naively thinking this would help quiet the engine a little and help reduce some white smoke...could these things be the culprits?

Thanks for the help and reassurance that the diesel forum isnt annoyed with every Newbie and his repeat threads.

rrgrassi · #8 08-22-2007, 10:35 AM

Do the valve adj on a weekend, or your next day off. It really is not difficult, just time consuming.

Bad fuel can be an issue. Add some PowerService stuff or Lubromoly to the fuel tank. I get diesel fuel at Wally world also, and have had no issues. There is always a line at the diesel pump. I also hit the truck stop on my route to an from work.

Stop leak is not a good idea, in any engine.

kerry · #9 08-22-2007, 10:35 AM

Do not remove the air filter permanently. It is just a test to see if there is a restriction in it.
EGR is an exhaust gas recirculation valve that allows some exhaust to re-enter the intake manifold. I'm almost certain you do not have one on a 76.

One clarification, if you're putting gas in the vehicle then we've found the source of your problem right there.

Sudden onset of black smoke is a certain indicator of a radical change in the air to fuel ratio. Either fuel or air delivery to your engine has changed. Did you leave a rag in the engine comparment that got sucked into the air cleaner? Did a squirrel build a nest in your air inlet.

Army-Ant · #10 08-22-2007, 11:30 AM

Im going to check the oil bath assembly this afternoon...
Since Im going to open it up, should I clean it out while Im in there? No one answered...should the oil in there match the engine oil I used? Last I checked, there was oil up to the line inside the bath, can I soak it up and add fresh oil? How crucial is it that the lid to the bath be tight? One of those snap-clamps is loose and wont stay down.

rrgrassi · #11 08-22-2007, 12:12 PM

The oil in the bath does not need to match the engine oil.

Was the smoking issue happening before or after you did a fresh oil bath? IIRC, there are some filters that replace the oil bath type, and they do not like oil. They will restrict air delivery big time if oiled.

If the lid is not on tight, unfiltered air can bypass the filter.

Palangi · #12 08-22-2007, 12:40 PM

How much oil is in the air cleaner?? It should only filled up to the arrow mark, which is about one inch.

The air cleaner is not fussy about what grade of oil is in it. Any cheap motor oil is OK.

junqueyardjim · #13 08-22-2007, 01:30 PM

Not only does it wreck your engine, but if you keep on talking about gas fuel for that car, some one will surely give you a gas fill up one of these days. Grown up guys with diesels don't use the word gas. You might have gas in your belly, but not in a diesel. Use diesel or fuel, and call it by it's proper name, never gas.

Army-Ant · #14 08-22-2007, 01:33 PM

Quote:

Originally Posted by Palangi

How much oil is in the air cleaner?? It should only filled up to the arrow mark, which is about one inch.

The air cleaner is not fussy about what grade of oil is in it. Any cheap motor oil is OK.

Its up to the arrow mark...when I first added fresh oil which was a day or 2 after I bought the car...everything in there looked pretty clean. The filter is a metal type filter with a handle. It looks original...not aftermarketish. The black smoke started 2 days ago after filling up. I hadnt tinkered with anything since changing the fuel filters (NAPA Gold brand) which was about 5 days ago.

So when I get the car home...remove the air filter, put the lid back on the oil bath, start the car up and let it idle and check for black smoke...it this my plan of attack?

winmutt · #15 08-22-2007, 02:03 PM

have you oiled you IP?