Reading Exhaust Smoke, basic Diesel diagnosis/Troubleshooting + related comments - PeachParts Mercedes-Benz Forum

whunter · #1 02-14-2013, 06:27 PM

This one is strange enough for special note...

http://www.peachparts.com/shopforum/diesel-discussion/335505-end-my-patience-1984-300d-issue.html

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BLUE SMOKE

* Excessive blue smoke usually indicates low piston cylinder compression, commonly caused by crankcase oil entering the combustion chamber, partial combustion, then out the exhaust.
* Worn piston rings.
* Scored cylinder wall.
* Valve guide/seal leak.
* Head gasket failure on an oil passage to cylinder.

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WHITE SMOKE smells like diesel:
Note: If slow cranking is not the problem !!!

* Air in the fuel system.
* Seriously contaminated or extreme (critically) low cetane diesel can cause white smoke.
* Valves out of adjustment (OM615, OM616, OM617 and all earlier diesel engines).
* Depending upon your ambient temperature, bad glow plugs or a faulty glow plug control module can cause or exacerbate white smoke during engine cold start up.
* Dirty injectors lean out the air/fuel mixture, causing loss of power, rough idle and sometimes, white exhaust smoke.
* When white smoke is still visible after full operating temperature, the engine may have one or more bad injectors, miss adjusted ALDA, retarded injection timing, a damaged timing device, or a worn/damaged injection pump.
* Low engine cylinder compression.
White smoke generally happens when there is not enough heat to burn the fuel.
The unburnt fuel particles blow out the tailpipe producing a rich, thick, diesel fuel odor.
It is normal to see white smoke from the exhaust during sub-zero and colder weather, at least until the engine warms up.

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WHITE SMOKE no diesel, or cloying sweet odor:

* Typically a coolant leak into one or more combustion chamber.
* Cracked head, bad head gasket, cracked cylinder.
* Usually a cooling system pressure test will eliminate all possible external issues, leaving mechanical diagnostic engine teardown the only option.

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BLACK SMOKE

* Black smoke is usually a sign that there's too much fuel, not enough air or injection pump timing is off.
* Leaky injectors will enrich the air/fuel mixture and cause black smoke.
* A restricted exhaust system.
* Leaking Turbo seal.
* Worn - damaged valve guides and or seals.
* Vacuum modulator diaphragm broken = transmission fluid pumping into the engine crankcase through the vacuum pump = potential engine runaway (please read this for more on this topic)

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Mechanical diesel injector failure has TWO root causes:
1. Fuel contamination/quality.
2. Structural failure.

MECHANICAL DIESEL INJECTOR PROBLEMS

X. varnish deposits.
X. Obstruction - Clogging.
X. Wear - erosion.
X. Leakage.
X. Weak spring - age.

You need a pop tester to check the opening pressure of the injectors for proper diagnostics..

IMO: The easiest way to find a seriously bad injector on a mechanical injection diesel is to loosen one line at a time with the engine running.
General Note: If while changing the glow plugs the ends are burned, check the injection timing because may be advanced to far.

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If you have not read these threads yet, please study them now.

Run away diesel, why does it happen?
http://www.peachparts.com/shopforum/diesel-discussion/101404-run-away-diesel-why-does-happen.html

Warning ALL Diesel Owners
http://www.peachparts.com/shopforum/diesel-discussion/309367-warning-all-diesel-owners.html#post2841158

Bad smelling fuel, what to do
http://www.peachparts.com/shopforum/diesel-discussion/94728-bad-smelling-fuel-gag-gasp-choke.html

Diesel owners need to know fuel data
Diesel owners need to know fuel data - PeachParts Mercedes ShopForum

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Brian Carlton · #2 02-14-2013, 06:31 PM

WHITE SMOKE:

Smells foul like burnt oil...........or worse.

1) Worn turbo seals or main bearings in turbo allowing significant amouts of oil to enter the airflow. Not all that noticeable at idle...........but very apparent when the airflow is increased.