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5-19
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
Is speed low only
in composite
operation?
Are other
attachment
speeds within
standard levels?
Does the
symptom change
when port relief
valve is replaced
with other valve?
Is pilot valve
normal?
Are LH/RH travel
speeds within
standard levels?
Is combination
of oil streams
normal at boom
hoisting and at
arm extrusion?
Are both LH/RH
travel speeds
low?
Is MCV pilot
pressure within
standard?
Does spool of flow
summation check
valve move lightly
by hand?
ͽ
;
Flow summation
check valve spool
is stuck.
Hydraulic pump is
faulty.
Ϳ
Port relief valve is
faulty.
Cylinder is faulty.
Control valve spool
is stuck.
Pilot valve is
defective.
Pilot relief valve is
faulty.
Gear pump is
broken.
Pilot valve is faulty.
Normal.
Disassemble and
repair.
Disassemble and
repair.
Disassemble and
repair or replace.
Disassemble and
repair.
Disassemble and
repair.
Clean pilot piping
interior or repair
piping.
Disassemble and
repair.
Disassemble and
repair or replace.
Disassemble and
repair.
Adjust engine
revolution.
Clean orifice in
control valve.
Clean pilot piping
interior or repair
piping.
Disassemble and
repair.
ͽ
;
Ϳ
B
BOOM, ARM OR BUCKET SPEED IS LOW
2)
Does control
valve spool move
lightly by hand?
Is not MCV pilot
pressure piping
clogged or is not
there oil leakage?
Is gear pump
delivering oil?
Is pilot piping not
clogged or is oil
not leaking from
the piping?
Is MCV pilot
pressure within
standard level?
Is primary pilot
pressure within
standard level?
Is engine
revolution within
standard level?
Is not orifice in
control valve
clogged?
Cause
Remedy
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
OK