Do 300Ds smoke more than 240Ds - PeachParts Mercedes-Benz Forum

240Joe · #1 08-08-2002, 06:57 PM

I have an 80 240D and an 83 300D. I've been working on what I believe is excessive smoke on the 300D. The car runs great, has excellent power, uses very little oil, and starts immediately. I've checked most of the things I know that could cause the problem but it still smokes more than my 240D.

Today while driving home, I followed another 300D down the highway. He was smoking about like I was. Whenever he got on the accelerator, you could see what looks like grey smoke. When he was running at a steady speed, the smoke disappeared. Very similar to mine.

For you guys with both cars, do you notice that the 300 emits more smoke than the 240? I'm beginning to think I might be trying to solve a problem that really isn't a problem.

thanks
Joe

84300DT · #2 08-08-2002, 08:47 PM

had some smoke (excessive) on my 300D and a valve adjustment cured it. also changed out the in line and spin on fuel filters which helped.

the_good_fellow · #3 08-08-2002, 11:47 PM

that's one cylinder difference

#4 08-09-2002, 07:22 AM

The smoke will be related to condition of the engine and injection system. One will be no more prone to smoke than the other.

My $0.02,

240Joe · #5 08-09-2002, 01:44 PM

Larry

I tend to agree with you. My 300D gets about 28.5 MPG and the 240D gets about 27, over the same roads/conditions. Both use about a quart in 1500 to 2000 miles, and neither leak oil. Both start well in the cold (down to 0 degrees F) but the 300D starts easier.

This is what I've checked on the 300D.

1. Injectors pulled and tested good at a good injection shop.
2. Injection timing adjusted from 17 BTDC to 23 BTDC (spec is 24 BTDC). This made about 1 MPG difference only.
3. Valves recently adjusted.
4. All filters changed (fuel, oil, air)
5. Done the Italian tune up multiple times
6. the fuel is good.
7. No signs of any coolent loss or pressure in the cooling system indicative of a cracked head.

The smoke that seems odd to me is after the engine is hot, I seem to get more smoke at idle. The smoke is grey like fuel, not blue like oil.

Any ideas what to try next??

thanks
Joe

CarolinaMBZ · #6 08-12-2002, 12:38 PM

Seems like the Turbodiesels smoke more than the normally aspirated. Whether its related to turbo specific adjustment issues, I don't know. Usually when I have seen a big puff it has been from a turbo.

Palangi · #7 08-12-2002, 09:12 PM

My 300D turbo puts out little or no smoke. With the 240D, if I coast down a little bit with it in gear, I can lose sight of the guy behind me in a black cloud. I dunno why.

leathermang · #8 08-13-2002, 09:31 AM

Most people stop at the injectors for some reason.. the injectors and everything else can be perfect.... but if stuff has built up in the tiny holes ( 7 of them ? ) in the precombustion chamber it doesn't do a lot of good inside the cylinder...and I don't know that it will be cleaned by Purge,,, since some flow is usually necessary through an orifice to clean it with fluids.... so if you have done everything else normal you could pull the precombustion chambers and examine/clean them.... over the years, before one bought one's car the tips of some glow plugs could have rusted off in there....but carbon soot is a more likely culprit in stopping up some of those holes...

240Joe · #9 08-13-2002, 12:43 PM

leathermang

How difficult is it to pull the prechambers.? I've done about everything else on my mercedes diesels, but never this. Isn't there a tool?

Any help is appreciated.

Joe

leathermang · #10 08-13-2002, 01:39 PM

There are two tools... one a screw device which sits on the head and pulls it... and a slide hammer type... the first can exert more pressure on a stuck precombustion chamber but is more expensive....I don't know if they can be rented...

Be sure to pull the glow plugs before you pull the precombustion chambers

(since they extend into them from the side of the block). I believe they just get gently hammered back into place after being cleaned or whatever....I would read the Factory Shop Manual before doing this process...