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Discussion Starter #1
I know there are lots of posts regarding smoke on cold starts, etc. but I couldn't find any pertaining to my setup. If there is one out there that I didn't see, I apologize in advance.

I drive a 96 2500 with the 5.9 Cummins of course. I have a little less than 192k miles on it. It has been in my family since it was purchased brand new in 1996. It has been very well maintained. With that being said, the only thing I have done to the engine performance wise is new injectors. I purchased some new Bosch 300HP injectors (part #0432133864) and installed them a few months ago. Now that the weather is dropping at night, it's usually around 35-40 degrees in the morning when I fire the truck up. I notice a lot of white/grey smoke with a very slight tint of blue. It would smoke a little when it was cold and not plugged in with the stock injectors, but it is much more noticeable now with the new injectors. Once the engine is warmed up, the smoke stops. Now I learned from other peoples posts that smoke when cold is normal. The only thing that worries me is the blue tint to the smoke. I know for a gasser engine, blue smoke is caused from oil getting into the combustion chamber by worn rings, valve guides, etc. But the Cummins uses no oil between changes. And once it's done warming up, there is no smoke at all.

My question is should I be concerned about what I call excessive smoke on the cold start? Although the smoke has a slight blue tint, it does not smell like burned oil. Just smells like diesel exhaust. I also have an old Mercedes diesel, which smokes quite a bit on a cold start, but never had a bluish tint. I suspect the new injectors have something to do with it. Does anyone have any advice? Should this be something I should worry about? Any information would be greatly appreciated!
 

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My 96 dose the same thing... dose it like to skip, spit and spatter and almost choke its self out if you try to drive it? Mine dose and cant seem to find out why... some say the timing has slipped and others say i have a fuel leek??
 

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Discussion Starter #3 (Edited)
No it runs and drives just fine. The idle is a bit on the rough side when it's cold. But tends to smooth out once the engine warms up a bit. Sometimes if I put the truck in reverse and haven't let it warm up enough on a really cold morning the engine will stall when I let off the accelerator. I countered that by bumping up the idle to about 900RPM during the cold months of the year. Turning the idle up helps starting in the cold plus helps it stay running (no need to keep your foot on the accelerator) and seems to work up a bit quicker if left to idle.

12v5.9, when is the last time you checked your fuel filter? I thought my timing had slipped before, almost the same symptoms your experiencing. Come to find out, the fuel filter was past due for a change. Changed the fuel filter and off I went. I would check the simple things first. If you suspect a timing issue, I have found a few posts on here before that explain how to check the timing yourself.
 

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I have replaced it about 4 times over the summer and still dose it... and i have seen the threads and i have a guy lined up to do it for me and I hope that it works!!!
 

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White smoke (raw fuel) with a hint of blue (raw fuel smoke will have a blueish tint in the cold) is somewhat normal. at temperatures above freezing, it is not.

unnecessary amounts of smoke could be caused by one or both of the grid heaters not functioning. The post-heat cycling of the grid heaters help greatly reduce white smoke at start up. Without even touching anything, its pretty easy to tell when both grid heaters are working as the volt gauge will drop to ~10v when you first turn the key and the grid heaters do the pre-heat cycle. If the gauge only drops to ~12v, you likely have only one GH element working.

Air in the fuel system can also cause excessive smoke as it lowers dynamic fuel timing (the actual injection event)

And last but not least, static (pump) timing being too low will cause the same symptoms.

All of these things will contribute to incomplete burns at startup, and its only going to get worse when the temperature drops.
 

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Discussion Starter #9
I think the smoke is just normal for the cummins and the injectors I installed. A friend of mine just installed the same injectors a few weeks ago. He has noticed the truck smokes a bit more as well. I know both grid heat elements are working as I checked them when the weather started to cool down. I had the local Cummins shop check timing before I installed the new injectors. The timing was right where it should be. So I am just going to say the smoke is normal and leave it at that. Thanks for the help everyone!
 

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When you installed the new injectors, you slightly retarded the timing. You didn't mean to, but you did. The reason is that the new injectors have a higher pop pressure than the used ones you took out. The higher the pop pressure, the longer it takes the injection pump to reach that pressure in the injector lines. End result: Very slightly retarded timing. Much if not most of the white and blue startup smoke can be eliminated by getting a couple of degrees more timing in the thing. Unfortunately, it takes some (not very expensive) special tools to do that. Leaving it the way it is won't hurt anything.
 

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Wow aren't those pretty large for a stock truck??
No not really. These are not performance injectors, they are factory bosch injectors, so the 300 hp rating is the bhp number, where as aftermarket injectors are rated as hp improvement over stock. so 300 hp aftermarket injectors are stock + 300.

Hope that helps. Clear as mud right?
 

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No not really. These are not performance injectors, they are factory bosch injectors, so the 300 hp rating is the bhp number, where as aftermarket injectors are rated as hp improvement over stock. so 300 hp aftermarket injectors are stock + 300.

Hope that helps. Clear as mud right?
Oh! I get it now! I've never heard of them being rated like that before, but it does make sense :thumbsup: I always thought they were rated over stock.
 

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Did you use the washers that were recommended for the new injectors?
Too thin or thick can cause smoke.

Even at below zero my trucks only smoke for 15-30 seconds max.
 
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