Cummins N14 STC, Celect, Celect Plus – Service Manual Engine Noise Excessive – Combustion Knocks

Engine is operating at low ambient temperature

Check the shutters and engine compartment air. Refer to the Operation of Diesel Engines in Cold Climates, Bulletin 3379009.

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 known high quality fuel. Refer to Fuels for Cummins® Engines, Bulletin 3379001.

Air in the fuel system

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

Coolant temperature is below specification

Refer to the Coolant Temperature Below Normal troubleshooting symptom tree in Section TS.

Static injection timing is not correct

Check the static injection timing. Refer to Procedure 006-025 in Section 6.

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.