Hitachi NR 90AC2 Technical Data And Service Manual page 17

Problem
Possible cause
< Output section >
Air pressure is too low.
Piston O-ring is worn or
damaged.
Piston bumper is abnormal
(dislocated, deformed or
damaged).
O-ring of the cylinder is
abnormal (dislocated,
deformed or damaged).
Driver blade is abnormal
(deformed, burrs, damaged
or fatigued).
Cylinder's internal surface is
abnormal (deposits of dirt or
worn).
Head valve sliding surface is
abnormal (galled, damaged
or needs oil).
Head valve spring is
abnormal (fatigued or
damaged).
< Control valve section >
Plunger (A), valve piston (B),
valve bushing (A) or valve
bushing (B) is abnormal
(galled or damaged).
O-ring is worn or oiling is
needed.
Inspection method
Pull the nail feeder
backward and perform idle
driving. Check if the driver
blade has returned.
Check if nails can be driven
2
at 5 kgf/cm .
While operating the nailer
without nails, check if the
drivng operation is
performed.
After operating the nailer
without nails, check if the
driver blade is kept in the
down position.
After making idle driving,
check if the driver blade is
kept in the down position.
Disassemble the control
valve and check the O-ring.
--- 14 ---
Remedy
Adjust for 5 to 8.5 kgf/cm
Replace the piston ring.
Replace the piston bumper.
Reassemble or replace.
Repair or replace.
Remove the dirt and apply
oil, or replace.
Replace the defective part.
Apply grease.
Replace the head valve
spring.
Replace the defective part.
Apply grease, or replace.
2 .