Crazy smoke related question??????

[Bug Out]

What, other then RINGS, causes the cummins to smoke heavy when cold and a little when warm?



It does have the fuel smell smoke when cold. . ( I love the smell of diesel in the morning!)



I guess what I'm trying to do, is eliminate all possibilities before a rebuild. .



thanks.



PS: On ocassion, it cranks like a gas engine with the timing advanced too far. . ?

 

[KBurgoyne]

mechanically injected truck smoke more than computer controlled since the timing is set. as for the smokin when cold. if its just start up smoke or some haze, that just happens its not a big deal. the engine doesnt reach peak thermal efficiency until it warms up.

how many miles are on it.

 

[cerberusiam]

What color is the smoke?

 

[Bug Out]

248K and smoke is gray

 

[AEdelheit]

Sounds like air might be getting into the system overnight, when you start it cold its got air and possibly missing and then the air bleeds out and runs ok, or possibly a bad injector leaking fuel into the cylinder overnight, has to burn off excessive fuel when cold before it clears up

 

[Bug Out]

It runs smooth and strong , more then i would guess a 160HP motor to do when cold or hot.



What is a sure fire way to know injectors are bad or how would injectors create the smoke?



Sorry i don't know this stuff yet, but never had an oldie like this one. All the others i owned ran without a burp.

 

[KBurgoyne]

a bad injector would slowly leak fuel into the bowl and sit there until start-up. the rich mix makes a lot of smoke when it finally ignites. at almost 250k, it might be best to just replace the injectors. stock replacements are 400, a mild set of aftermarkets arent. much more. check to see if the lines are tight. they toque to 17lbs just do it by feel if its really loose it will be noticeable look for fuel around the base of the lines.

 

[Bug Out]

Ok. I'll try that. Another reason that has me looking away from rings was the blow by tube is not putting out much blow by. Correct me if I'm wrong, but worn rings allow for a lot of blow by.



Could a plugged blow by tube be some of the problem? There is some coming out of the dipstick when you pull it out but not a lot. . ?

 

[DVolk]

Id try a bottel of good injector cleaner / anti gel as well

 

[JLEONARD]

Cummins does have a "blowby test" that they recommend as the only test to determine if the rings are shot. (I have that write up someplace). A compression test is not recognized as a valid test.

Some blowby thru the dip stick tube is normal. You probably have a gunked up vent pipe/plumbing. My ex truck would show signs of this when I ran it hard (too much boost).

The marine Cummins guys use the truck oil fill tube as a venting port. They basically put on a very small "K&N" style filter on it and trap the blowby yuck in a conveniently placed bottle.



My guess is that at 248 K miles you have some or all of the injectors leaking or spraying a bad pattern and when the cylinders are cold all of the fuel cannot be burned. I would think it is time for injector service, either rebuilding ($60 to $80 each) or new.

If you think your engine is smooth now, wait until you do either. It will be silk.



By the way, the "backyard" blowby test on a marine 6BT(A) is to unscrew the oil fill cap (which is on #1 valve cover on a marine B) let it sit on the hole at idle. If it stays the blowby is acceptable. If it blows off, you can start ordering parts.

 

[cerberusiam]

248K and smoke is gray

Gray or more bluish? That is pretty normal on a cold start and until the engine warms up. Its just uncombusted fuel from the cylinder temps being low.



If you have the same problem when the engine is up to temp then it is time to start digging.



To test blowby for potential problems, loosen the oil cap until it just sets on the VC. Run the eninge up to about 160 rpms and watch the cap. If it is bouncing around and you can see a discharge there are problems.

 

[Greenleaf]

My 1990 smoked grey with original fuel injectors at 320-some thousand when it was cold. Unless your engine was operated w/o an air filter, a rebuild will be the last thing that engine needs. These are not gas jobs where you pull the engine at 240,000 cuz it's had enough.



BTW/FWIW, I gave my 90 a "tune-up" at well over 300k miles.

 

[Bug Out]

I think I will wind up selling it for now. I'd love to keep it, but dont have the room or time to do what I want. Its a solid truck and runs good, looks good etc.





All of the sudden the HOA is sending me letters etc. Must have gotten a neighbors panties all tied in a knot... .

 

[Greenleaf]

HOA >>>>>>>>>> ?? Isn't that the (exhaust) smoke police organization out there in AZ?

 

[Bug Out]

wasnt about the smoke. Had to juggle junk around and truck was where it was not supposed to be.



Thats why next year I'm buying a NON-HOA home. .