SEAL-CAMSHAFT 3973209 - Caterpillar

Truck EnginesTroubleshooting failures that include fuel dilution, engine misfire and/or combustion gas leakage into the fuel system, may lead to the discovery of cut, eroded or missing unit injector O-ring seals. This condition may be the result rather than the cause of the failure.
Follow these steps during repair procedures.
1. Check the sides of the injector cone for carbon above the seat area. If carbon is present, check the seating surface of the sleeve inside the bore of the cylinder head. If the surface is rough or grooved, resurface the sleeve using the reamer provided in the 4C4054 Service Tool Group (see Special Instruction, SEHS9120, "Removal and Installation of Unit Injector Sleeve"). Care should be taken to keep chips from the reaming process out of the combustion chamber. Application of liberal amounts of grease on the tip of the reaming tool is an effective method of containing chips. Remove only enough material to provide 360 degrees of cleanup at the seat area.2. Prior to assembly, apply a liberal amount of STP ® to the injector O-ring seals. STP is effective in "cut-free " installation.3. Tighten the injector retaining bolts to 28 5 N m (22 4 lb ft).