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Black smoke


Blakloks
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I just lifted this off the merc forum, these are the responses to a guy asking "what colour is unburnt Diesel?" this is what 4 different peoples opinions look like :yahoo:

"un burnt diesel has a grey/white/blue colour and a distinctive sickly smell,"

"Unburnt diesel will be black, "

"Unburnt diesel appears white. Poorly burnt diesel appears black
"

"I would discribe un burnt /poorly burnt diesel .... white or pale blue colour, not as blue as burnt oil though."

 

 

 

Below is the response I agree with, I was a forklift engineer for many years and I believe this to be correct from ChrisBrad66 on the MB Club Forum (i hope he doesn't mind me lifting it :good: )

 

 

you only get black smoke when your air filter is blocked or some other restriction on the induction side,causing a rich mixture, i.e. too much fuel and not enough air, bluey white smoke is unburnt or poorly burnt fuel. However a small puff of smoke every now and then when you accelerate could just be the exhaust clearing itself out, all diesel engines will do this now and again

Edited by sishyplops
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As an ex plant engineer (diggers and dumpers not Daisy's and pansies) black smoke is over fuelling or Unburnt diesel , white smoke is water so indicative of a head gasket problem and blue smoke is oil leeching past the piston rings and burning. Black smoke suggests changing the air filter, checking the cold start system isn't stuck on or could be a lazy turbo on the way out and the carbon build up inside it burning off when you boot it and it spools up and gets hot

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I think you will find the above incorrect, its probably the valve stem seals, they become hard and do not seal anymore, this allows oil to drop into the cylinders, causing black smoke. More often than not black smoke is oil in the cylinder, not un burnt fuel.

Thats odd!

 

When I see a vehicle that blows it's rings it fills the road with a dense cloud of blueish smoke! Not black. Infact I remember an old girlfriends son topped the oil up in her car once! A whole 5L can :no: and when she started it, the whole street filled with blue/white smoke. The oil was being forced past the piston rings and directly into the cylinder.

 

When the valve stem seals went on my cars the smoke again was blue!

 

The ONLY time I ever had black smoke was down to the fuel air mixture :yes:

 

I have never seen a car spew out black smoke because the valve stem oil seals have gone or because there was oil finding it's way into the cylinder :no:

Edited by Lord Geordie
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I suggest it may be the injector adjustment - too much fuel for the air mixture resulting in unburnt fuel and 'black smoke'. Air filter check first (as others have said), check pipes for restrictions etc. it could simply be a tweek on the EMS and if you car is a well known type, a 5 min diagnostic will sort it.

Edited by Kes
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Drive it like you stole it around the bloke if it clears it's just **** and you shouldn't worry. If it blows up don't blame me lol.

 

This is why modern diesels go into to safe mode and make you drive em at 2000 revs for so many miles. Or when ya put the puter on to do a dpf clean it holds the revs at 3000 rpm for a prolonged time.

 

Karpman

 

Oil burning is blue

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Lol, I love the way that so many people are confident and certain about what they post but in reality don't have a clue

Repair, sell diesel estates for a living. Mainly vauxhall and up until recently ex mod cars. It smokes when he boots it. A quick check of the stick should give him an answer to if it is burning oil or not. And when they start to burn some with the fuel they sure get through it.

 

Karpman

 

Plenty of vids of cars on youtube with valve stem seals gone kicking out blue smoke

Edited by karpman
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Thanks to the guy that supported me on it being oil, 22 years as an army VM working on nothing but diesel wagons should have taught me something. white smoke is coolant , blue is to do with over fueling, or bad air filter, BLACK is oil.

TTFN

No disrespect bud! But I too spent many moons working on cars! I agree, white is normally water finding it's way into the cylinders.

 

Black smoke was nearly always due to lack of service and maintanance and was blocked air filters.

 

Blue smoke was ALWAYS either shot rings! Degraded or failed valve stem oil seals or oil finding it's way into the cylinders.

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