5-18 2) BOOM, ARM OR BUCKET SPEED IS LOW YES YES Are other YES attachment speeds within Is combination Is speed low only standard levels? of oil streams NO in composite YES normal at boom YES operation? hoisting and at Does spool of flow summation arm extrusion? check valve Is travel speeds NO move lightly by within standard hand? NO NO levels? YES Is travel speeds NO low? YES Is MCV pilot pressure within NO standard? NO OK Does the symptom change YES when port relief valve is replaced Does control with other valve? YES NO valve spool move lightly by hand? Is MCV pilot NO ⓐ pressure within standard level? YES Is not MCV pilot pressure piping clogged or is not NO there oil leakage?
NO YES Is primary pilot NO Is gear pump ⓑ pressure within delivering oil? standard level? NO Is engine NO ⓒ revolution within standard level? YES Is not orifice in ⓓ control valve YES clogged? Is pilot piping not clogged or is oil NO not leaking from the piping? Is pilot valve NO normal? NO Cause Remedy ⓐ 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. ⓑ Flow summation check valve spool is stuck. Hydraulic pump is faulty. ⓒ ⓓ 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.