Section C - Engine Noise

Perform the Pre-Diagnostic Troubleshooting Procedure before proceeding.

When standing in front of the vehicle with engine running, several distinct noises may be heard. These noises may vary depending on listener location, 2WD vs. 4WD, engine temperature and miles on the vehicle.

1. Gear Train Noise Evaluation

a. Normal: Gear noises noticeable when standing in front of the engine, may vary from engine to engine.

b. Abnormal: Gears are visually damaged or have backlash or end clearance out of specification. The cause should be identified and corrected.

2. Fuel Pump Noise Evaluation

a. Normal: Pumping noise may vary - the fuel pump is producing between 5,000 and 20,000 psi depending on operating conditions.

b. Abnormal: A fuel pump with excessive pressure variation (+/- 500 psi from set point) is abnormal. The cause should be identified and corrected. Refer to Engine Surge or Engine Difficult to Start symptoms.

3. Injector Noise Evaluation

a. Normal: Combustion noise may vary at different operating conditions. Maybe more noticeable on throttle tip-in and vary from engine to engine.

b. Abnormal: Loud knock with smoke and vibration. Cylinder cut out test or mechanical blocking of injectors (Special Tool # 9011) should be used to identify failed injectors.

4. Valve Train Noise Evaluation

a. Normal: Valve settings are correct and no visual damage to parts.

b. Abnormal: If valve settings are out of specification, they should be reset. Also, correct any damage to rocker levers, push rods, or cross heads.

5. Refer to the detailed diagnostic information available in TechCONNECT under:

Service Info tab > 9 - Engine > Diagnosis & Testing > Engine Diagnosis - Mechanical.