Home » Duramax LLY » Duramax LLY – ENGINE DIAGNOSIS – Black Smoke

Duramax LLY – ENGINE DIAGNOSIS – Black Smoke


1. Low grade diesel fuel.

2. Over rich fuel mixture:
– Drain/return lines restricted.
– Injector(s) stuck open.
– Engine speed or throttle sensor fault.

3. Black smoke at wide open throttle.


1. Drain and refill tank.

2. Test, diagnose and repair as required.

3. Restriction in air intake system, no vacuum to wastegate actuator, damaged wastegate, or air leak at intake or exhaust manifold.

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