how much blasck smoke should i expect

[brutherb]

How much black\grey smoke do you guys get when the transmission downshift and bumps up the rpms say from cruising at 1500 to 2200-2500. I just got my truck on the road and i got quite a bit.

 

[Stangshcky12]

Stock I don't think you should see that much
I have a manual transmission and the only time I ever see black smoke is when I run out 3rd and 4th gear and blow some of the carbon out, once the trucks cleaned out itll only leave a bit of a haze

 

[BigSloth]

In a diesel, black smoke is soot from fuel. Generally speaking, the more fuel the more smoke. Does the truck have a tuner? upgraded injectors?

If not, a stock 5.9 shouldnt smoke excessively.

 

[Trupiano]

How many miles? If it's not tuned deleted, then that's bad. Possibly a blown head gasket symptom... But we don't have to jump to conclusions yet.

El phono

 

[Stangshcky12]

My first thought is bad injector(s)
You'll usually hear a taping with that too

 

[BigSloth]

Yeah my first step in jumping to conclusions would also be a leaking/bad injector. That will cause excessive smoke rather quickly and like ^ he said a tapping noise usually. That's more so when they completely die off. A mildly leaky injector can smoke a lot before it causes any noticeable sounds or loss of performance. But leaky injectors in common rail applications tend to descend from leaky to dead rather quickly, so you'll soon have a tapping, then a misfire and tons of smoke.

 

[brutherb]

thanks guys the truck is new to me, but had some front end body damage. So i wasn't able to see it running before i got it. Today was my first test drive. No tapping at all, and the previous owner said it was a rebuilt motor. He apparently burnt a hole through one of the pistons. Didn't ask how. I will take it to the local diesel shop and have them take a look.

 

[brutherb]

ps 200,000 kms. no water in the oil so i don't suspect head gasket. run and starts fine, but i have no experience with cummins so i don't know how they should act.

 

[Stangshcky12]

I'm guessing there isn't any fuel in the oil then either?
A leaking/bad injector can wash out the rings/cylinder walls too and the excess heat created from extra fuel can possibly melt a piston

Wouldnt hurt to check for blow by by loosening the oil fill cap, if it rattles/jumps around then you have problems
That's pretty low mileage so it shouldnt be a problem

 

[DannyMK2]

on occasion, ill see a good puff of black smoke if i hit it merging on the highway. no grey smoke. grey smoke is usually a sign of a bad injector. how is your air filter? when i first bought my dually it would smoke more often. the air filter was filthy and once i changed it the amount of smoke i saw went down.

 

[NWRQC]

Is the truck tuning stock? That can make the difference between needing to look into it or not.
As mentioned black smoke is unburned fuel which can be caused my several things. A hot tune will cause smoke because they usually fuel heavy. A clogged air filter can cause it, a dirty MAP sensor as well. I would think if it was an injector it would smoke more then just when the engine RPM jumps up from a downshift or accelerating quickly.
I would check those things first....

 

[brutherb]

thanks for all your posts guys, i found one of the flex boots on the air inlet pipe was torn badly letting the compressed turbo air just leak into the engine bay, but it would have been dumping the same amount of fuel, so as someone wrote that it is a sign of unburned fuel. So I drove and got a new boot yesterday from the wreckers about to install it. Can you believe that piece from the dealer is $280, i drove 2 hrs each way to a wrecker to get the part for $40. Things we do....

 

[NWRQC]

Glad you got it figured out and fixed! Good info for others with a similar issue.