Machine Moves Neither Forward Nor Backward 2/2; Machine Moves In One Direction Only (Forward Or Backward); Slow Machine Speed Or Small Drive Force 1/2 - Sakai R2-4 Shop Manual

TROUBLESHOOTING

3-2-1. Machine moves neither forward nor backward 2/2

Check point
9. Propulsion Pump
10. Parking Brake
Solenoid Valve
11. Brake Inlet
Pressure
12. Flange

3-2-2. Machine moves in one direction only (forward or backward)

Check point
1. F-R Lever Linkage
2. Multifunction Valve

3-2-3. Slow machine speed or small drive force 1/2

Check point
1. Bypass Valve
2. F-R Lever Linkage
3. Charge Circuit
Pressure
4. Suction Filter for
Steering • Charge
Pump
10-068
Cause
Discharge flow rate is insufficient due to
efficiency degradation of propulsion pump.
Discharge flow rate is insufficient due to
wear of propulsion pump drive shaft splines.
Propulsion circuit pressure is not held in
propulsion pump case.
Brake remains applied because spool of
parking brake solenoid valve does not shift.
Brake cannot be released because brake
inlet pressure is low.
Drive torque is not transmitted to pump due
to faulty flange.
Cause
F-R lever linkage is faulty.
Low circuit pressure due to incorrect high
pressure relief setting or internal leakage of
multifunction valve.
Cause
Bypass valve is slightly open.
F-R lever linkage is faulty.
Stroke of propulsion pump swash plate
is small because charge pressure is low,
decreasing discharge rate of propulsion
pump.
Insufficient steering • charge pump
discharge.
Charge pressure decreases due to internal
leakage of solenoid valve connecting oil
supply circuit with charge circuit.
• Parking brake solenoid valve
• Speed change solenoid valve
Flow rate of steering • charge pump
decreases as well as charge pressure
decreases due to clogged filter.
Check/Action
• Measure discharge flow rate of propulsion
pump with flow meter.
• If discharge flow rate is not within specified
range, repair propulsion pump or replace it
if necessary.
Replace propulsion pump.
If pressure in propulsion pump case is not
within allowable range, repair propulsion
pump or replace it if necessary.
Repair parking brake solenoid valve or
replace it if necessary.
• Measure brake release pressure.
• If low, repair or replace propulsion motor.
Replace flange.
Check/Action
Check and adjust F-R lever linkage or
replace it if necessary.
• Interchange two multifunction valves.
• If faulty condition is accordingly reversed,
check and adjust multifunction valve or
replace it if necessary.
Check/Action
Close bypass valve completely.
Check and adjust F-R lever linkage or
replace it if necessary.
• Measure charge pressure.
• If low, check and adjust charge relief valve
or replace it if necessary.
Repair steering • charge pump or replace it
if necessary.
• When solenoid is energized, check if oil
flows in return circuit to tank.
• If oil is flowing, repair solenoid valve or
replace it if necessary.
Clean suction filter or replace it if necessary.