Overhaul of Fuel Injectors
When overhauling fuel injectors it is important that the work area is very clean. Lay paper out on the work bench, disused charts are ideal. Do not use rags or cloths for cleaning components. Wash all items thoroughly in kerosene and blow dry with compressed air.
Inspect all sealing faces for any damage. Small scratches can be removed by lapping in against a special surface plate, using a fine lapping paste such as jewelers rouge. Any pitting or indentation of the sealing face mean the nozzle should be replaced or sent to specialists for reconditioning.
Clean the nozzle bore with a special drill and use specially supplied needles for cleaning the nozzle holes. If the holes are too large, or appear oval when inspected with a magnifying glass, the nozzle should be discarded.
The nozzle needle and guide are matched a pair and should not be interchanged. The needle should be free to move in the guide and when lifted it should drop down into the guide under its own weight.
Reassemble the injector and tighten the cap nut down to the correct torque. Note that some engine manufacturers supply different sets of nozzles for the same engine. An example of this would be slow steaming nozzles, which may have different size holes. Always make sure the correct nozzle has been fitted.
"Operation and Maintenance of Machinery in Motor Ships" by N.E. Chell