den

My 300D sat for a couple days, when I started it, it ran rough and there was much white smoke. After a min. or so it cleared up and ran just fine. The second time that same day I had white smoke and rough running at start up.
What will cause this situation? Any thoughts, suggestions?

sosh

Have never owned a diesel benz, however, I have owned and operated numerous diesel engines in boats that I have owned. This smoke is most likely unburned fuel on start up. The cause is most likely a leaky injector and that would also contribute to rough running until it seals itself up with fuel pressure. Could be dirt or carbon in the injector. On my boats I never worried about it just so it cleared up and smoothed out shortly after start up. If it bothers you have your injectors checked or replaced.

sph17

I never had this in any of my MB diesels (three W123 and a W201), but in a 77 Honda I had, white smoke indicated another blown head gasket with engine coolant leaking into the cylindar to be "burnt" and expelled as white vapor.

Are you loosing engine coolant, is the level droping?

Steve Clark

If you're lucky,you may have a glow plug or two that isn't doing its' thing.The white smoke is probably unburned fuel...as soon as the cylinder(s) with the dysfunctional glowplugs get warm,the injected fuel behaves as it should by burning instead of going out the exhaust as fuel vapor.

If you're not lucky,the vapor could be water from a leaking head gasket.Is your coolant level dropping?.

den

Water level staying right on, must have been something with the injector leaking or ?? Drove it today and all is well ?????????
Thanks

den

den

That was interesting. Anyway this white/blue smoking at start up is back. As soon a GP light goes off the car starts right up and runs smooth for abt. 20 sec. then the rough idling and the smoke. As soon a temp gets up to 40/60 C the car quits smoking and runs just fine. No coolant in oil, no oil in coolant, car uses no oil. Smoke has a heavy fuel smell so would this be an injector leakin into the cylinder after the car sits for half a day or over night? What about a GP relay kicking out too soon and leaving the engine to warm itself up? Start ups when warm there is no smoke at all, only when a cold start up. Any thought on a couple diesel surge cans to clean out the injectors? Could some small dirt particles be stuck in an injector causing it too weep a bit of fuel?
Lots of questions.
Thanks

sosh

Its most likely not the glow plugs. They are starting aids only (on any diesel). Its most likely an injector. They do wear out. Replace all injectors and it will most likely be fine. Cleaning does not allways work. Go to a good diesel shop or MB dealer and I am sure they can help you out. The danger of continuing to use the car as it is, is that assuming raw fuel is the culprit it is washing down the cylinder walls when it malfunctions and that can cause very serious problems

Sambsamb

Note!
Blue smoke = Oil been burned
Black = fuel..
White = Water..!

Seems to be leaking water.

sosh

You are correct for a gas engine but not a diesel

Sambsamb

Sosh youre right. For water and oil it should be the same, but about diesel i dont know...

sosh

Water white mist will not go away but will continue as long as the engine is running. With a diesel, white could be water, however its usually unburned fuel and smells like it. This is usually an injector problem on one cylinder but could also be a cylinder thats way down on compression. With a Detroit Diesel you can disable each injector with the engine running to see which cylinder or injector is the problem as the smoke will stop when that injector is disabled.

jcollingridge

Top 10 Diesel Tech Tip...
I've owned a lot of Mercedes diesel (115/123) cars. The glow plugs are
definitely something to check out. There is a fast glow plug relay and glow
plugs that heat quicker and the relay stays on up to two minutes after the glow plug light goes out. Much quicker starts, starts in much colder temperatures than OEM glow plugs and the common smoke problem from a cold diesel engine will likely disappear.

Tip Of the Day...before you spend alot of time and money take the car to a long steep hill and put your foot into it. Most folk lug a diesel engine which is the absolute worst thing you can do. If you are a city driver, every so often take the car out and run it hard up a steep grade. Let the temperature rise to it's higher "normal temp. range" with your foot on the floor boards. Check the rear view mirror and delight in the black cloud of smoke you are creating...it will clean itself out if done with conviction and full intent.
Have the courage to keep your foot into it with the rpm and heat range up there!!! Dr. Marshall Booth and other MBZ enthusiasts affectionally refer to this practice as giving the diesel an Italian Tuneup. Many a suspect running diesel Mercedes has been sold as a parts car when all it needed to run like a fine Swiss clock was an Italian Tuneup:-) Jim <collingridge@cariboo.bc.ca>