My truck now has a steady stream of black exhaust even at idle, not opaque black, but black. Black enough to burn your nose and water your eyes! There is no white smoke when the engine is cold, in fact the black smoke starts almost instantly after start up. Engine starts easy, has same power as before.
Changing the air filter and the fuel filter made zero difference. Three different tanks of fuel with two cans of Sea Foam per tank has made zero difference. Truck has one knocking injector thats been knocking for 40,000 miles.
I'm thinking it's not turbo or intercooler related because our engines don't produce boost at idle. I'm thinking it's not CP3 or lift pump because engine starts easy, runs the same as before and gets same mileage as before (usually 19-21 hwy).
Is there anything on our engines that can enrich or lean the air/fuel ratio based on engine temperature, similar to what gas engines have?
Engine oil has no smell of diesel fuel.
Could a dying injector do this?
Anyone have an idea what to repair?

 

I'm curious as well! My truck is doing the exact same thing and has been for the past 50k miles or so. Since it has been running well, I never thought anything of it. I'm sure the Cummins guru's will chime in soon.

 

Oh buddies that's bad news on a cummins diesel black smoke at idle. Simple truth is one of two things. If your idle is erratic and loping it is most likely injector related if you got white smoke. If your idle is smooth you have a oil ring issue and hopefully the cyclinder walls are not scored. Either way the beauty of the cummins is it is so easy to work on. Pull the valve cover, yank the injectors and have a injection shop check them out. If their okay unbolt the head and dig deeper. Black smoke at idle in my experience is always ring related. Usually caused by glazed cyclinder walls/worn oil seal rings.

 

A friend of mines 03 lopes pretty good on cold start and sometimes hot idle.IF he uses a BIG dose of fuel additive it runs fine.Withen a tank of no additive it starts the lope thing again.No smoke! 140k on ther clock.Any thoughts.Just started this about 5k ago.

 

That sounds a tad serious... Could you explain deeper on glazing, and why they wear? I traded my '01 Cummins with a little under a quarter million miles on her and she never smoked, when she wasn't supposed to of course... I have around 115k on the '04 and have used synthetic ever since after the break in period, and keep it changed between 8k and 10k miles. I'm just trying to figure out where all the wear is coming from and why I would have ring failure already. Like I mentioned above, it has had the black smoke at idle for about 50k now. Maybe I could just run it till catastrophic failure on the ISBe and replace it with a P pumped 12 valve. If I only had the know how...

 

Without a visual inspection of the piston rings and cylinder walls it is all guessing as to what is the cause of black smoke at idle. Does the turbo shaft seals check out okay? How much does your oil level drop between changes? That's I can think of. Hope you find the source.

 

It sounds more like inj. leaking to me.Burned oil is usually a blueish color,not really black,& coupled with a few inj's. knocking I'd think you have a few leaking nozzles.If it was mine I'd pull the inj's.& have them recon'd/replaced.If it's been going on for a long time it has possibly washed the cyl's down with diesel,& caused glazeing also,which will eventually cause your catastrofic failure..02 from a Cummins tech.

 

Assuming injector leakage, which part fails, the mechanical half or the nozzle? I pray it's the nozzle half, that way I would have an excuse to get some EDM's. I've had 3 replaced in the past, last time they produced massive amounts of white smoke. I don't have the frequently talked about injector knock, well not after warm I should say. It does for 5 minutes or till warm, but after warm everything seems normal. Maybe one of you guru's that are going to the Nats. in Indy can listen to it and give it a once over.

BTW, how long before a cylinder wall becomes glazed, and is it reversable?

 

My first posting so here goes. My 04 3500 started smoking at idle about 200k, Had a overhead run by dealer. Valves adjusted no more smoke.

 

That's a perfect first post, thanks for the hope! I would really, really hate for my tires, and SBC funds be depleted because I have to buy new injectors...


BTW, welcome to the greatest site ever! There are several Cummins guru's on here, unfortunetly i'm not one of them...

Once again, WELCOME!

 

You can try to adjust the valves.(They should be adjusted about every 500 eng.hrs.=about 30,000 miles.)If that cures your problem thats great,but if it doesn't I would still look into the injectors.The part that I think may be leaking is the nozzle.It will continue to leak past the needle as long as the rail pressure is high enough to make it leak.(Most of the time if not all the time)The nozzles on the common rail engines are essentually the same as on the previous generations.The electronics are on the top.If one of those fails it will either be fueling ALL the time the rail pressure is up,Or it will not fire causing a miss.BTW valves will sound like a tappet on a gas motor.

 

Map sensor = bad.

 

The 12 valve adjustment was every 50k and ours(3G) are 130k heavy work or 150k light work.Of course you can adjust them any time you want. I will say my New Holland tractor called for 600 hours and I found all valves slighly tight.It did REDUCE smoke to nothing after adjustment.

 

no 6 oh no you da man! It was the map sensor. I cleaned it with brake-kleen and no more smoke. Thanks!

 

That's good to hear, it may also net you a little extra MPG as well. I'l try cleaning mine tomorrow, hopefully it will do me some good...