Excessive smoke out of the NHC 250

smittyjr355 · Nov 28, 2011

Just got the M817 home to find out that it smokes a lot!! The engine runs good, lots of power, starts right up. When the truck is idling white smoke pours out of the exhaust no matter wether the engine is cold or has been running for an hour! Once the engine has a load on it the smoke turns black. This tells me the engine is getting to much fuel so I checked the temps on each cylinder to see how they compare. I found that the first cylinder was about 50 degrees cooler than the rest. I am guessing the injector is bad but would like to get some more input before I start replacing parts!!

wdbtchr · Nov 28, 2011

White smoke is an indicator of moisture getting into the cylinder.

indy4x4fab · Nov 28, 2011

wdbtchr said:
White smoke is an indicator of moisture getting into the cylinder.

He's right, this would also exspane the cooler cycinder. check your coolent level as well as you could do a compition check on the engine. Harber feight sells a diesel compression tester that works well, I have one.

Now if you still think you may have a bad injector. There's a diesel shop in Muncie, IN, that's called "Dave's Diesel" or I'm sure you "Clark Truck'' up there by you, could check the injector for you. All you would have to do is remove the injector from the engine and take it ti a diesel injection shop and they could pressure test the injector for about 25 dollars and if it is bad then they can also rebuild it or them for you at half or less then half the cost of buying new.

smittyjr355 · Nov 28, 2011

White smoke also means raw fuel that inst being burnt correct? Almost any diesel smokes white when first being started because of the cold temp of the motor and fuel not being burnt completely? You can definitely smell the raw fuel as well.

indy4x4fab · Nov 28, 2011

indy4x4fab said:
Now if you still think you may have a bad injector. There's a diesel shop in Muncie, IN, that's called "Dave's Diesel" or I'm sure you "Clark Truck'' up there by you, could check the injector for you. All you would have to do is remove the injector from the engine and take it ti a diesel injection shop and they could pressure test the injector for about 25 dollars and if it is bad then they can also rebuild it or them for you at half or less then half the cost of buying new.

Then remove the injector and have it tested. Start small or simple and work to bigger or more expensive.

73m819 · Nov 28, 2011

If you are getting unburnt fuel smoke after warm up be careful, running like this will wash the rings, putting fuel in the oil, burning the rings, major ware on the sleeves/cylinders

smittyjr355 · Nov 28, 2011

yes I plan on fixing the problem before driving the truck too much. Just curious if anybody else has had the similar problem.

patracy · Nov 28, 2011

What does the exhaust smell like? Coolant will smell sweet. White unburnt fuel will tend to make your eyes burn and smell more like fuel.

indy4x4fab · Nov 28, 2011

smittyjr355 said:
White smoke also means raw fuel that inst being burnt correct? Almost any diesel smokes white when first being started because of the cold temp of the motor and fuel not being burnt completely? You can definitely smell the raw fuel as well.

Here's your sign. :jumpin:

smittyjr355 · Nov 28, 2011

yes the smoke smells like fuel and will make your eyes water and will also get you dirty looks as you smoke people out!!! :driver:

mckeeranger · Nov 28, 2011

If you want to start with the easiest, simplest, cheapest first, check the adjustment of the cylinder one injector. If it has backed off a little, it may not be closing the injector all the way, thus feeding fuel all the time.

Just a thought.

http://test.steelsoldiers.com/upload/809/TM9-2320-260-34-1.pdf
Starting on page 3-244
You will need an inch/pounds torque wrench.

EMD567 · Nov 28, 2011

On my M814, Cold is Blue smoke.

73m819 · Nov 28, 2011

EMD567 said:
On my M814, Cold is Blue smoke.

valve guides

swbradley1 · Nov 28, 2011

White smoke on my 818 is a head gasket and you can tell it has antifreeze coming out in vapor form.

I hate to think what it did to my lungs backing it into the barn............

:-(

augiedoggy · Nov 28, 2011

I agree with others, sounds like too much fuel getting in there. Definetly check that oil level, and test the engine oil on your skin, you can tell if it has fuel in it(very thin and will wick out the cracks in your skin quickly). I had colder #! and #6 cylinders manifold temps but I think that is normal as the inner cylinder manifold runners have more heat running through them so they will get hotter than outer most cyls. You could try swapping an injector from a known good cylinder to the one in question.
You can do a power balance test with your rocker covers off by holding each injector closed with a socket and extension while running.
Injector adjuustment is critical as I found out!

Check this thread for my similar troubles and good luck!

http://www.steelsoldiers.com/5-ton-up/73256-nhc250-valve-injector-overhead-adjusting.html

nk14zp · Nov 28, 2011

First thing to do is adjust the valves and injectors.
Edit augie beat me to it.

indy4x4fab · Nov 28, 2011

augiedoggy said:
I agree with others, sounds like too much fuel getting in there. Definetly check that oil level, and test the engine oil on your skin, you can tell if it has fuel in it(very thin and will wick out the cracks in your skin quickly). I had colder #! and #6 cylinders manifold temps but I think that is normal as the inner cylinder manifold runners have more heat running through them so they will get hotter than outer most cyls. You could try swapping an injector from a known good cylinder to the one in question.
You can do a power balance test with your rocker covers off by holding each injector closed with a socket and extension while running.
Injector adjuustment is critical as I found out!

Check this thread for my similar troubles and good luck!

http://www.steelsoldiers.com/5-ton-up/73256-nhc250-valve-injector-overhead-adjusting.html

He's right, you may get really lucky on this one.

augiedoggy · Nov 28, 2011

indy4x4fab said:
He's right, you may get really lucky on this one.

Thanks Indy, lessoned learned the hard way are not easily forgotten!

smittyjr355 · Nov 29, 2011

After reading the service manual, I noticed there are two different torque specs for adjusting the injector depending if the injector is a top stop or not. Being that the truck is a 1971 I am assuming that my motor does not have top stop injectors?? Thanks for all the help!

augiedoggy · Nov 29, 2011

smittyjr355 said:
After reading the service manual, I noticed there are two different torque specs for adjusting the injector depending if the injector is a top stop or not. Being that the truck is a 1971 I am assuming that my motor does not have top stop injectors?? Thanks for all the help!

smitty, please read this thread: Nhc250 valve injector overhead adjusting

It will answer all of your questions. It is information from the guru of all things Cummins, Will Wagner :doh:

Excessive smoke out of the NHC 250

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