Black Smoke at altitude

[RichM]

Question for Weave or anyone else who has experienced a lot of Black Smoke pouring out when the engine is working hard, when climbing a 6% grade at about 7000-9000 feet.Last month I spent a lot of time out west and while climbing up I 17 near Flagstaff AZ a trucker behind me said I was really smoking black. Then later on I was coming up on Raton Pass on the New Mexico/Colorado border at about 9000 feet and I could see the black smoke again inb a cars headlights behind me. When I ran at relatively lower altitudes and goosed it up a hill I saw no problems. I thought it might be the turbo having some blowby at higher altitudes. I spoke to Cummins and thd they said I might have had too much oil in the engine(could be as I just had a change) or dirty injectors etc.I have a Cummins C Series 225 HP with 522,000 + on it,still gets great mileage,uses no oil and pulls good.Just wondering if I need to have something else to worry about.Any Info would be appreciated.

 

[NEVERHOME247]

MIGHT CHECK YOUR AIR FILTER. DIRTY AIR FILTER WILL CAUSE TRUCK TO BLOW BLACK SMOKE.

 

[Weave]

Your older C8.3 has mechanical fuel injection. As altitude rises, the air becomes "thinner", containing less oxygen. This will cause your diesel engine to run richer as the injectors are squirting the same amount of fuel but there is less oxygen in the air/fuel ratio. This richer mixture causes the black smoke. There is really nothing you can do about it, it's normal. Trucks with computerized engines (the cummins ISC is the newer computer version of your engine) have a sensor that makes adjustments to the injection pulses to compensate for altitude, the reason you don't see the newer trucks smoke so much. Regardless, I still prefer Bosch mechanical injection over the computers for reliability.