Cummins ISX11.9 CM2250 – Service Manual Engine Noise Excessive – Combustion Knocks

Engine is operating at low ambient temperature

Check the winterfront, shutters, and under-the-hood air. Use under-the-hood intake air in cold weather. Refer to Cold Weather Operation, Bulletin 3387266.

Ether starting aid is malfunctioning

Repair or replace the ether starting aids. Refer to the OEM service manual.

Fuel grade is not correct for the application or the fuel quality is poor

Operate the engine from a tank of high quality fuel. Refer to Procedure 018-002 in Section V of the Operation and Maintenance Manual, ISX11.9 CM2250, Bulletin 2883444.

Air in the fuel system

Check for air in the fuel system. Refer to
Procedure 006-003 in Section 6
.

Vibration damper has failed

Remove the vibration damper and operate the engine at the rpm where the noise normally occurs. If the noise is still present, proceed to the next step. If the noise is eliminated, replace the vibration damper. Refer to
Procedure 001-052 in Section 1
.

Coolant temperature is below specification

Refer to the Coolant Temperature Below Normal symptom tree.

Injector(s) are malfunctioning

Perform diagnostics to find the damaged injector(s). Replace the injector(s) as necessary. Refer to
Procedure 006-026 in Section 6
.

Overhead adjustments are not correct

Measure and adjust the overhead settings. Refer to
Procedure 003-004 in Section 3
.