B5.9G, B5.9LPG – Troubleshooting and Repair Manual – Engine Runs Rough or Misfires

Symptom Tree  t062

This is symptom tree t062
Cause Correction

Electronic fault codes active or high counts of inactive fault codes

Refer to Section TF in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118, for fault code troubleshooting.

 

Condition occurs only at idle

Refer to the Engine Runs Rough at Idle symptom tree.

 

Engine is cold

Allow the engine to warm to operating temperature. If the engine will not reach operating temperature, refer to the Coolant Temperature is Below Normal symptom tree.

 

Coil wire malfunctioning

Remove wire from engine and use a digital multimeter to measure resistance across the wire. Refer to Procedure 013-012.

 

Ignition coil malfunctioning

Check the ignition coil. Refer to Procedure 013-012.

 

Spark plug(s) damaged or incorrect gap

Inspect plug(s). Refer to Procedure 013-016.

 

Ignition system harness connector pins bent or damaged

Inspect harness. Refer to Procedure 019-196 in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118.

 

Battery voltage is low or bad ground connection at battery

Check the batteries. Check the battery circuit. The battery cable ground must measure within OEM specifications for voltage drop under electrical load. Refer to Procedure 013-007.

 

Fuel leak

Check the fuel lines, fuel connections, and fuel filters for leaks using the combustible gas detector service tool. Refer to Procedures 005-003, 005-047, and 005-052.

 

Low or no fuel pressure at the mixer (secondary pressure)

Use an electronic service tool to measure the fuel pressure after the gas mass flow sensor and before the mixer. Refer to Procedure 005-047.

 

Low or no fuel pressure at the fuel filter (primary pressure)

Use an electronic service tool to measure the fuel pressure at the fuel filter. Refer to Procedure 005-061.

 

Oxygen sensor offset parameter is not correct

Verify that the offset parameter on the oxygen sensor tag matches the oxygen sensor offset parameter listed in INSITE™. Refer to the INSITE™ User’s Manual, Bulletin 3885798.

 

Heated oxygen sensor is damaged or has drifted

Use INSITE™ to check for significantly improved engine performance with the system in open-loop operation. Refer to the INSITE™ User’s Manual, Bulletin 3885798.

 

Oil from the fuel has accumulated on the gas mass flow sensor, screen packs, or elsewhere in the fuel system

Check for oil in the fuel system. Refer to Procedure 005-009.

 

Engine position sensor (EPS) is not installed correctly

Check the engine position sensor for correct installation. Refer to Procedure 019-038 in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118.

 

Engine position sensor (EPS) damaged

Check the EPS. Refer to Procedure 019-038 in the Troubleshooting and Repair Manual, Fuel Systems and Electronics, B5.9G, C8.3G, L10G-III, Bulletin 3666118.

 

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 Fuels for Cummins Engines, Bulletin 3379001.

 

Overhead adjustments are not correct

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

 

Camshaft is damaged

Inspect the camshaft for damage. Refer to Procedure 001-008.

 
Last Modified:  05-Jan-2004