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turbodiesel
New Member
USA
3 Posts |
 Posted - 02/17/2006 : 11:30:04 AM
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I know that it is very hard to diagnose a problem without actually seeing/working on it first hand. Just curious for some feedback from those experienced with the Detroit 671's...
What would be some likely causes of a turbocharged Detroit 671 (1986) smoking and running rough?
Engine leaks oil and might be leaking some diesel as well when running. I can imagine that a worn/leaking turbo compressor oil seal could cause the smoke. Also, I can can imagine faulty injectors possibly causing smoke and rough running.
What do you think might be some other possible causes?
I don't have any experience on Detroit engines and actually trying to diagnose a problem on someone else's '86 Crown. I believe it has close to 200K miles on it.
Thank you very much.
Ed |
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ModMech
Top Member
USA
948 Posts |
Posted - 02/17/2006 : 5:13:12 PM
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Ed, what color is the smoke?
The very first thing to do is determine the fuel quality, next check the fuel pressure. |
If you want customer service, you NEED an International! |
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turbodiesel
New Member
USA
3 Posts |
Posted - 02/17/2006 : 6:48:41 PM
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I would call the smoke color gray.
Here's a picture of the smoke while idling:
Thanks for any insights you might have. |
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mrbluebird
Advanced Member
USA
381 Posts |
Posted - 02/17/2006 : 7:13:24 PM
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| i agree with turbodisel |
YOUR CHILDREN'S SAFETY IS OUR BUSINESS |
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ModMech
Top Member
USA
948 Posts |
Posted - 02/18/2006 : 09:22:09 AM
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I am decidedly NOT an expert in the "Two Stroke Joke" department, but based on what I see the timing is late or just incomplete due to low compression on one or more cylinders.
I diagnose diesels by exhaust smell, color and volume. With only one for my three data points, and unfamiliarity with the 2 strokes in general, I can only guess. I would set the overhead (rack), and see what happens.
But, fuel QUALITY can cause this too, I would start by running it on KNOWN GOOD FUEL, and see what you get.
Low fuel pressure will result in a gray FOG, and I do mean FOG. Low Cetane will cause hard starting and fog as well.
Reatarded timing will cause gray fog is minor, blue fog is significant.
Timing is a function of lash on most pushtube activated (mechanical) fuel injectors like these.
An injector that is leaking can also cause gray exhaust, but you WILL have a "cold" cylinder. If they are all very similar in exhaust temp, suspect fuel/tune up issues. |
If you want customer service, you NEED an International! |
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wagonmaster
Top Member
USA
2298 Posts |
Posted - 02/20/2006 : 03:56:50 AM
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A two stroke Detroit Diesel will smoke heavily after extended idling, or when cold, warming up. You post mentions neither, however it isn't clear exactly what you are dealing with. Once at operating temperature (180*) drive the bus and see what it does. Does it continue to smoke while driving, under load, or does it clean up? These aren't "clean" engines anyway, but they are very reliable when properly maintained and will pull hard to the governor speed.
Joe |
Joe
Land of the Free, because of the Brave! |
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Dravo
Senior Member
USA
93 Posts |
Posted - 02/20/2006 : 5:31:01 PM
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| We used to joke that if a 671 smokes that means it's running! Did you ever swap a head on those and get all those little gaskets and washers to lineup? But they did pull, especially at night when the air was cool, you could get an old GM4104 to fly 80mph. |
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wagonmaster
Top Member
USA
2298 Posts |
Posted - 02/21/2006 : 05:28:56 AM
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quote:
GM4104
Boy,
There's a model from the past....PD4104. The predecessor to the famous scenicruiser(PD4501), even used the same front end and dash, etc. I drove one many times during my Greyhound years, long ago...The originals had two valves oer cylinder, but the replacements engines came with four valves per cylinder and lots more power! Turned sideways and leaned way over, they were fun to work on, too! Point taken though, the two strokes were smokers..... |
Joe
Land of the Free, because of the Brave! |
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cowlitzcoach
Advanced Member
USA
325 Posts |
Posted - 02/22/2006 : 1:04:47 PM
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The cause of a DD 2-cycle running rough could be as simple as a rack out of adjustment to a bad cylinder.
If it is also leaking fuel it could be a bad injector.
The smoke you have pictured is not unusual for any DD 2-cycle, parictularly when cold (my 6-71T smokes like a mosquito fogger when first started when the ambient temperature is below 40 degrees. The smoke one observes when the engine is up to operating temperature is more important.
If it smokes blue, you are burning oil--most likely some bad rings.
If it smokes black, you are over fueling--most likely low compression or a rack way out of adjustment.
If it smokes white, you are in a lot of trouble--most likely getting coolant into the combustion.
One problem that arises, particularly in motorcoaches, is drivers don't put the engine on fast idle. A DD 2-cycle will eat itself up if you slow idle for extended periods of time. The heat of combustion will not burn up all of the fuel and the excess fuel will dilute the lube oil. That will, in time, cause excess wear on the cylinders and liners causing premature failure.
As far as the leaking oil goes, if it isn't leaking oil it is out of oil. Few DD 2-cycle engines don't leak. The question is how much is it leaking and from where is it leaking?
You mention the bus is a 1986 Crown. At a guess I would venture to say the engine has never had anything done to it. If that is the case it may just be a worn out engine and it is time for an inframe.
Good luck.
Mark O. |
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Topic |
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Detroit 671 Smoking
