B5.9G, B5.9LPG, B Gas Plus, B LPG Plus – Engine Speed Surges at Low or High Idle

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 101-007 (Electronic Controlled Fuel System) in Section 1. If fault codes are active, contact a Cummins Authorized Repair Facility.


Engine is cold

Allow the engine to warm up for approximately 1 to 3 minutes. Refer to Procedure 101-015 (Operating the Engine) in Section 1.


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.


Battery voltage is low

Check the batteries and the unswitched battery supply circuit. Refer to the OEM service manual.


Accessory load is excessive for the idle speed setting

Reduce the accessory load or increase the engine idle speed. Refer to the OEM service manual.


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.


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.


Intake air restricted

Inspect and change air cleaner. Look for other restrictions. Refer to Procedure 010-059 (Air Cleaner Restriction) in Section 4.


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:  16-Feb-2005