Symptoms

Black smoke or smoke under load

What causes it depends on the engine. 5 documented failures on 5 engines list this among their signs. Pick your engine for the causes ranked, how to tell them apart and the usual fix.

6.7 Power Stroke (2011-present) 1 known cause: Piezo injector wear and fuel dilution of engine oil 5.9 Cummins (1994-2007) 1 known cause: 12v overflow valve weak (hard start / low power) 6.7 Cummins 2007-2018 1 known cause: Holset VGT turbo sticking / actuator failure Duramax LB7-LMM (2001-2010) 1 known cause: VGT turbo vane carbon / actuator wear (LLY+) Duramax L5P (2017-present) 1 known cause: Injector wear / pigtail-connector misfires

Built from the failure-mode records on this site: a failure is listed when its own symptom list describes this sign. Engines not shown have no documented failure with it in our records. How we tier and source facts.