PIN 1483465 - Caterpillar

3408E (7PR),
3412E (4CR) EnginesDuring unit injector replacement in the above engines, cleanliness is very important when dealing with the area around the unit injector case and sleeve bore. All carbon deposits should be removed from the unit injector case around, and including, the lower O-ring seal groove. Carbon deposits should also be removed from the 120 degree included angle surface at the bottom of the unit injector sleeve. Failure to properly clean these areas may cause an improper seal at the lower unit injector O-ring. This could directly result in unit injector failure due to leakage of combustion gas into the fuel passage.
Fine grade "Scotch Brite" material is the preferred cleaning material. It is available from the Tools And Shop Products Guide in roll form as 1U-5512 Cut/Polish Roll and sheet form as 8T-7765 Hand Pad.
Illustration 1: Typical Unit Fuel Injection Pump Sleeve. (1) 120 degree included angle surface where the lower injector O-ring seats.
Illustration 2: Typical Unit Fuel Injector. Entire lower portion of injector should be clean, especially (2) lower O-ring groove and adjacent surface.The preferred method of cleaning the sleeve bore is:
* Place a 38 mm (1.5 in) square piece of "Scotch Brite" material on the end of 9U-6862 Small Tapered Brush.* Hold and twist the brush with 4C-5027 Tap Wrench against the lower sleeve bore surface.
The use of power tools to rotate the material should not be necessary since carbon in this area is not as difficult to remove as at locations exposed to higher temperatures.* The surface should be cleaned until it is smooth and shiny. The entire sleeve bore should, then, be cleaned to remove any loose carbon particles.
It is advantageous to use 4C-6774 Vacuum Kit Gun, which is operated by compressed air, to clean the bore.