Usage:
3176 (2YG, 7LG) Truck Engines
Description of Change: A new combustion seal (3)is used in the unit injection group. See the illustration. This new O-ring seal reduces combustion gas leaks between the unit injector cone and the brass sleeve in the cylinder head. It is recommended that a new combustion seal be installed each time a unit injector is installed in the cylinder head.
Location of components. 9X7557 O-ring Seal (1). 9X7722 O-ring Seal (2). New 9X73717 O-ring Seal (3). Unit injector cone (A). Unit injector tip (B).
Adaptable To: The new 9X7317 O-ring Seal (combustion seal) is used in the unit injection pump group. The new seal is adaptable to 3176 Truck Engines, 2YG1-Up, 7LG1-Up Use the procedure that follows to install the new combustion seal.
Combustion Seal Installation Procedure
Reference: Special Instruction, SEHS9246, "Using the 4C4054 Unit Injector Sleeve Replacement Tool Group. "
1. Carefully clean the surface of the unit injector in the area where the new combustion seal is to be installed. Be sure to clean both the both the outside diameter of tip (B) as well as the bottom face of cone (A). Use a soft bristle brush (such as a toothbrush or an 8S2258 Brass Wire Brush) to remove the carbon deposits. Mild (hand or dish) soap can be used to soften the carbon deposits.
NOTE: Use care not to damage the edge of the cone or the orifice holes in the tip when cleaning parts. DO NOT use a steel wire brush or a wire wheel of any sort because they can damage the tip and cone.
2. Install new combustion seal (3) by sliding it over tip (B) of the unit injector until the seal contacts the bottom face of cone (A).
3. Use a 4C4054 Sleeve Replacement Tool Group to ream the brass sleeve in the cylinder head. See the Reference. If a new sleeve has been installed or there is evidence of a combustion gas leak on the seat, use machinist layout blueing to check the seat.
NOTE: The new combustion seal DOES NOT eliminate the need to ream the brass sleeve in the head. All sleeves MUST STILL be reamed prior to installing the unit injectors in the cylinder head.
4. Lubricate only O-ring seals (1) and (2) with STP Engine Oil Treatment before installing the unit injector in the head. New combustion seal (3) does NOT require lubrication. Tighten the injector clamp bolt to a torque of 33 N ·m (24 lb ft).