B5.9G, B5.9LPG, B Gas Plus, B LPG Plus – Engine Runs Rough or Misfires

Symptom Tree  

Fuel level is low in the tank

Fill the supply tank. Refer to the OEM service manual.


Electronic fault codes are active

For instructions on how to read active fault codes, refer to Procedure (Electronic Controlled Fuel System) in Section 1. If fault codes are active, contact a Cummins Authorized Repair Facility.


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.


Fuel leak

Check the fuel lines, fuel connections, and fuel filters for leaks using the combustible gas detector service tool. Refer to a Cummins Authorized Repair Facility.


Ignition coil malfunctioning

Check the ignition coil. Refer to Procedure 013-012 (Ignition Coil) in Section 6.


Spark plug(s) damaged or incorrect gap

Inspect plug(s). Refer to Procedure 013-016 (Spark Plugs) in Section 6.


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 the OEM service manual.


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 a Cummins Authorized Repair Facility.


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 (Fuel Recommendations and Specifications) in Section V.


Overhead adjustments are not correct

Measure and adjust the overhead settings. Refer to Procedure 003-004 (Overhead Set) in Section 6.

Contact a Cummins Authorized Repair Facility

Last Modified:  15-Feb-2005