ISBe/ISB Series Engines – Engine Speed Surges at Low or High Idle

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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 Diagnostic Fault Codes in Section 1. If fault codes are active, contact a Cummins Authorized Repair Facility.

 

Fuel supply line restriction between the fuel pump and the injectors

Check the fuel supply line from the fuel pump to the cylinder head for sharp bends that can cause restrictions. Refer to a Cummins Authorized Repair Facility.

 

Air in the fuel system

Check for air in the fuel system. Tighten or replace the fuel connections, fuel lines, fuel tank standpipe, and fuel filters as necessary.

 

Vehicle parasitics are excessive

Check the vehicle brakes for dragging, transmission malfunction, cooling fan operation cycle time, and engine-driven units. Refer to the OEM service manual.

 

Fuel grade is notcorrect for the application, or the fuel quality is poor

Operate the engine from a tank of high-quality fuel. Refer to Section V.

 
Contact a Cummins Authorized Repair Facility
Last Modified:  22-May-2002