CYLINDER GP-BOOM 3891041 - Caterpillar

3114 (5EF, 1ZG, 4KR) Industrial, 3114 (6AF, 5JG) Generator Set, 3116 (2WG, 4PG, 5EN, 2MR) Industrial, 3116 (4KG, 1SK) Marine, 3116 (2SG, 1NJ) Generator Set, 3126 (9ZR, 6MS) Industrial, 3126 (8NM, 6SR) Marine EnginesReference: Troubleshooting Guide For The 3100 Family Of Diesel Engines With Mechanical Unit Injectors, LEVN4032, (45 minute Video).The lower O-ring seal has been removed from the fuel injector group. See the illustration. Tests indicate this O-ring seal is not an effective seal after a few hours of operation. This seal can take up a portion of the clamping force when the injector in installed in the cylinder head. When the seal deteriorates, this could lessen the clamping force holding the injector in position.
Until all injectors with the lower O-ring seal are depleted from inventory, it is suggested that the lower O-ring seal be removed when installing a new or remanufactured injector in the engine.
The area that seals the combustion gas from the fuel is the area of metal to metal contact between the injector cone and the sleeve. It is recommended that the sleeve be reamed whenever an injector is removed.
To confirm that a good seal exists between the injector and sleeve, use a 2P-8278 Air Fuel Tube Assembly (Plastic Sight Glass) in the fuel return to tank line after the injector installation. Use the sight glass while the engine is running to determine if there is combustion gas leakage. A steady stream of small (pencil point size) bubbles, or one pea sized bubble every 2 to 3 seconds is acceptable.
If there are any more air bubbles than that, use the diagnostic procedure recommended in the Reference Troubleshooting Guide to isolate and repair the leak.
Location of the O-ring seal to be removed from the fuel injector group.