Cummins N14 STC, Celect, Celect Plus – Service Manual Engine Runs Rough at Idle

Idle characteristics of CELECT™ and CELECT™ Plus systems are different than characteristics of the PT® system

Normal performance. No corrections are necessary.

Electronic fault codes active or high counts of inactive fault codes

Refer to Procedure 019-362 in Section 19 of the CELECT Plus™ Systems Troubleshooting and Repair Manual, Bulletin 3666130, or the CELECT™ Systems Troubleshooting and Repair Manual, Bulletin 3666084.

Coolant temperature sensor is malfunctioning

Check the coolant temperature sensor. Refer to Procedure 019-019 in Section 19 of the CELECT Plus™ Systems Troubleshooting and Repair Manual, Bulletin 3666130, or Procedure 019-019 in Section 19 of the CELECT™ Systems Troubleshooting and Repair Manual, Bulletin 3666084.

Electronic control module (ECM) calibration is malfunctioning

Verify the ECM calibration is correct. Check the calibration revision history for applicable fixes to the calibration stored in the ECM. Refer to the calibration history spreadsheet on QuickServe™ Online or the INCAL™ CD-ROM. Compare the calibration stored in the ECM with the engine rating and the Control Parts List (CPL), Bulletin 4021328. If necessary, calibrate the ECM. Refer to Procedure 019-032 in Section 19 of the CELECT Plus™ Systems Troubleshooting and Repair Manual, Bulletin 3666130, or the CELECT™ Systems Troubleshooting and Repair Manual, Bulletin 3666084.

Engine idle speed is set too low (mechanical fuel systems)

Adjust the fuel pump idle speed. Refer to Procedure 005-029 in Section 5.

Engine idle speed is set too low (electronically controlled fuel systems)

Verify the correct idle speed setting. Increase the idle speed with INSITE™ electronic service tool.

Engine is operating above recommended altitude (STC engines only)

Derate the engine by 4 percent for every 300 meters [1000 feet] of altitude above 3600 meters [12,000 ft]. Refer to the Engine Data Sheet.

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 Operation of Diesel Engines in Cold Climates, Bulletin 3379009.

Fuel supply pressure is below specification

Measure the fuel supply pressure.

Air in the fuel system

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

Fuel pump pulsation damper is cracked

Inspect the fuel pump pulsation damper. Replace the pulsation damper if necessary. Refer to Procedure 005-031 in Section 5.

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.

White smoke is present

Check the STC plumbing to each cylinder for restriction or loss of flow. Refer to Procedure 006-045 and Procedure 006-046 in Section 6.

Engine mounts are worn, damaged, or not correct

Check the engine mounts. Refer to Procedure 016-010 in Section 16 and the OEM service manual.

Overhead adjustments are not correct

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

Injector is malfunctioning (CELECT™ and CELECT Plus™)

Perform the automated cylinder performance test. Replace injectors as necessary. Refer to Procedure 006-026 in Section 6.

Injector is malfunctioning (PT/STC)

Remove and check the injectors. Replace injectors as necessary. Refer to Procedure 006-026 in Section 6.

STC injector top link is not correct

Compare the injector top link part number to the injector parts listing. Refer to Procedure 006-025 in Section 6.

Camshaft end clearance is excessive

Check the camshaft end clearance. Refer to Procedure 001-065 in Section 1.

Cylinder head valve leak

Check the cylinder head for fuel leaks between the valves and valve seats. Refer to Procedure 002-004 in Section 2.

Internal engine damage

Analyze the oil and inspect the filters to locate an area of probable damage. Inspect for damaged crankshaft, pistons, and liners. Refer to Procedure 007-083 and Procedure 007-025 in Section 7.