Yuchai YC4D60-D21 - Low injection pressure; Injector oil leak

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Low injection pressure
① Pressure adjusting screw
looseness
② Pressure adjusting spring
crack
③ Pressure adjusting spring
deflection
④ Spring seat and stem
damage
⑤ Needle stuck
Readjust and tighten the stud.
Check and replace.
Check and replace.
Repair or replace the damaged parts.
Clean and grind it.
Injector oil leak
① Bad seal of needle precision
pair
② Needle stuck
③ Nozzle retaining nut
damage and deflection
④ Sealing surface of injector
body and needle body
damage
Grind it after cleaning, replace it if ineffective.
Clean and grind, replace it if ineffective.
Replace it.
Lap in pair after cleaning, replace it if it can not
be reconditioned.