COIL AS 1912128 - Caterpillar

(1) O-ring.(2) Injector group.(3) O-ring. Before installing an injector, lubricate O-ring seals with clean engine oil. Install the injector according to the procedure in the Disassembly And Assembly Section of the Service Manual. Check and/or adjust the following: injector synchronization, fuel setting, fuel timing, and valve clearance, according to the procedures given in the Testing And Adjusting Section of the Service Manual. O-ring (3) is to provide initial sealing until the unit injector seats in the brass sleeve in the cylinder head. The injector seats in the sleeve almost immediately after the initial engine start. Therefore, deterioration of the O-ring will not result in combustion leakage. It is normal for this seal to deteriorate over time due to exposure to the hot combustion gasses. When the unit injector is removed, both the body O-ring seal (1) and the tip O-ring seal (3) should be replaced. The seating surface of the brass sleeve should be inspected and replaced if necessary.