3116 and 3126 Truck Engines Problem Loud Combustion Noise (Sound)

Probable Cause(s):

* Air In Fuel System
* Low Quality Fuel
* Defect In Unit Injector(s)
* Mechanical Problem
* Excessive Injection Actuation Pressure
* Cold Mode Operation
* Engine Timing Incorrect

1. Air in fuel system:

With air in the fuel system the engine will normally be difficult to start, run rough and release a large amount of white smoke. Find the air leak in the fuel system and correct it. If air is in the system, it will generally get in on the suction side of the fuel transfer pump. Refer to Problem 34: Air In Fuel.
2. Low quality fuel:

Check fuel quality. Refer to Truck Performance And Driveability Diagnostic Guide LEBT3477. If fuel is of low quality then remove the fuel from the fuel tank. Install new fuel filter. Put a good grade of clean fuel in the fuel tank.
3. Defect in unit injector(s):

Using an electronic service tool check for logged or active diagnostic codes. Refer to 3100 HEUI Diesel Truck Engine Electronic Troubleshooting, SENR6566, for Injector Solenoid Circuit Test.
4. Mechanical problem:

Find and correct the problem. The problem may be incorrect valve adjustment, sticking valve, or other internal problem.
5. Excessive injection actuation pressure:

Using an electronic service tool check for logged or active diagnostic codes. Refer to 3100 HEUI Diesel Truck Engine Electronic Troubleshooting, SENR6566, for Injection Actuation Pressure Test.
6. Cold Mode Operation:

Monitor any of the electronic service tool Status screens to verify the engine has shifted out of Cold Mode. An Active Cold Mode is indicated in the upper corner of any of the Status Screens. Check the engine after it has had a chance to warm up.
7. Engine timing incorrect:

a. Using an electronic tool check for logged or active diagnostic codes. Refer to 3100 HEUI Diesel Diesel Truck Engine Electronic Troubleshooting SENR6566, for Engine Speed/Timing.

b. If the engine has undergone repair involving the cam gear then Refer to Disassembly And Assembly, SENR6553, for the proper procedure for camshaft removal and installation. The cam gear is keyed to the camshaft. If the gear is installed correctly, it is nearly impossible for the timing to be off enough to cause knocking.

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