3114, 3116 and 3126 Engines Caterpillar

Engine Misfires, Knocks, or Is Unstable (at Idle Only)

Usage:

AP-1000 1HD

Probable Causes

Incorrect low idle setting
Faulty unit injector
Problem with the governor
Poor fuel quality
Air in fuel

Recommended Repairs

Incorrect Low Idle Setting

Verify that the low idle speed setting is correct.

Faulty Unit Injector

Inspect the unit injectors. Refer to Troubleshooting, "Unit Injector Misfire" and Troubleshooting, "Unit Injector".

Problem With the Governor

Ensure that the governor is operating properly. Refer to Troubleshooting, "Governor Instability".

Poor Fuel Quality

Ensure that there is good, clean fuel in the tank. When possible, interview the operator in order to determine if fuel quality is in question. Try to determine if the engine started misfiring soon after refueling. Refer to Troubleshooting, "Fuel Quality".

Air in the Fuel

Check for air in the fuel system. Refer to Troubleshooting, "Air in Fuel".

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