PeachParts Mercedes-Benz Forum - do clogged injectors=blue taolpipe smoke?

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do clogged injectors=blue taolpipe smoke?

heard this today from a former mechanic. he said an accompaning loss of power occurs when the injectors are clogged and the tailpipe smoke is blue?

this is a diesel schoolbus non mb(but we are getting mb engined buses in the near future).

any truth?

Quote:

Originally Posted by 83-240D

blue/white smoke from exhaust is always oil burnig....

clogged injectors would have either white smoke or black smoke along with a heavy odor of fuel in the smoke.

83-240D,

Seems like clogged injectors would not cause smoke from the exhaust. If an injector was not injecting fuel the engine would miss fire on that cylinder and only air would come out of the cylinder.

White smoke from the exhaust it actually unburned fuel, fuel that has not ignited. I don't see how a clogged injector would cause unburned fuel to get into the exhaust sine it isn't injecting any fuel.

Just my logical conclusion.

P E H

thanks fellas.

i thought that idea was wrong. loss of power would then be caused by the rings getting a little wide reducing compression and allowing oil into the cylinder. i will ask the driver about hard starting also.

I've seen "clogged" injectors that still pass fuel -- dripping instead of spraying. In that case you get nailing and black smoke from unburned fuel.

http://www.freeautoadvice.com/diesel/smoke.html

Here is a link to a diesel exhaust color analysis article. It is not the best one that I have seen but it was high on the google list. Google will probably give you better.

I googled:diesel diagnostics smoke color

Quote:

The first category is blue-white smoke:

Blue-white smoke may be noticed at engine start-up whether the engine is at normal operating temperature or not. Blue-white smoke can be observed at all ambient temperatures and should not last longer than a minute or two after the vehicle has been driven. Blue-white smoke can return when ambient temperature is below 10 degrees C (50 degrees F), and after the engine is warmed up due to extended idling. This is due to combustion chambers cooling own during periods of extended idling time. Heavy blue-white smoke may also occur if the engine is operated at full throttle with the transmission in neutral or park. If you see continuous Blue-white smoke while driving, then you probably have air being sucked into the fuel system.

The second category is white smoke:

White smoke and blue-white smoke share some of the same characteristics. White smoke is fuel not being burned. Extreme white smoke can be caused by the combustion chambers cooling down. One cause of this could be incorrect injection pump timing. Coolant getting into the combustion chamber can cause white smoke also. Possible causes are blown head gaskets, cracked heads cavitation, etc.

The third category is black smoke:

Black smoke is caused by an over rich mixture and normally occurs whenever the engine is working hard. Like going up a steep grade, being loaded heavy or during heavy acceleration. More black smoke can be observed when the vehicle is operated at higher altitudes because the air is thinner. A dirty air filter is also another cause of excessive black smoke. If black smoke is noticed while the engine is idling at low altitude or under normal driving conditions this condition should be diagnosed a.s.a.p. to prevent engine damage.

The fourth category is blue smoke:

Blue smoke is not normal and you do not want to be driving behind a truck that produces it. Blue smoke occurs when oil is entering the combustion chamber and is burning along with the fuel. Blue smoke usual indicates a condition which should be corrected a.s.a.p. Blue smoke also smells like oil burning. Possible causes include valve seals or cracked piston rings.

Quote:

Originally Posted by Old300D

I've seen "clogged" injectors that still pass fuel -- dripping instead of spraying. In that case you get nailing and black smoke from unburned fuel.

wqe got a couple of those too. i had one friday and i sat for 2 min revving the motor to get it warm enough to get over 20. then the smoke went away.

the blue smoke from unburnt diesel and the blue smoke from oil consumption is not easily distinguished in my experience. the way to tell one from another is to look at how and when it is smoking.

otherwise the above list of symptoms etc is excellent.

very informative

I have recently been dealing with some unusual smoking with my 300CD, maybe someone can shed some light on.

For the last few months, when it was cold out, I'd start the car in the morning and let it idle about 5-10 minutes. After backing out of the driveway and on the first acceleration, a nice BIG cloud of white smoke with some blue tint would exit the car. The rest of the time, it produced no visible smoke. It will still do this.

With in the last two weeks, I've noticed when I'm sitting at a light it will start smoking heavily untill I pull away, and then no visible smoke, only at idle. There also doesn't seem to be a pattern to it, as in it doesn't do it everytime I come to a stop. The last time it did it was yestarday when I came to stoplight after about 10 miles of Interstate driving between 70-80mph.

Its really starting to bug me. Thanks for any advice...

Quote:

Originally Posted by Old300D

I've seen "clogged" injectors that still pass fuel -- dripping instead of spraying. In that case you get nailing and black smoke from unburned fuel.

In our injectors what clogs are the tiny holes drilled through the pintles. The fuel is supposed to inject through the holes. When the holes clog the hydraulic pressure abnormally lifts the pintle off of its seat and the fuel injects through the abnormal opening between the pintle and its seat. The car will actually run quite well like this but you will get cold start nailing, smoking, uneven idle and many of the symptoms in the common complaints.

http://www.peachparts.com/shopforum/diesel-discussion/122334-tech-specs-injectors-torque-bar-pressures.html

More info and some links in this thread.