Sakai SW880-1, Shop Manual

Page: 417 / 428

11-207
TROUBLESHOOTING
3-2. Propulsion System
If a problem occurs in the propulsion systems such as the propulsion pump, propulsion motor and brakes,
determine the cause and carry out action as required, according to the following general troubleshooting items.
(NOTICE)
When checking whether or not the pressure is correct, refer to the pressure standard value for each
hydraulic circuit.
3-2-1. Machine moves neither forward nor backward 1/2
Check point Cause Check/Action
1. Oil Level of
Hydraulic Oil Tank
Oil level in hydraulic oil tank is low. Fill tank until correct oil level is obtained.
2. Bypass Valve Bypass valve is open. Close bypass valve.
3. Propulsion Charge
Circuit Pressure
Propulsion pump does not discharge oil
because charge pressure is low.
Measure charge pressure.
If low, check and adjust charge relief valve
or replace it if necessary.
•
•
Charge pressure decreases due to pressure
leakage from pressure cut off valve.
Check and adjust pressure cut off valve or
replace if necessary.
Insufficient steering • charge pump
discharge.
Repair steering • charge pump or replace it
if necessary.
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
•
•
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.
•
•
4. Propulsion Pump
Proportional
Solenoid Valve
Propulsion pump cannot discharge oil
because oil does not flow into servo cylinder
chamber due to faulty propulsion pump
proportional solenoid valve.
Measure pressure in servo cylinder
chamber. If low, repair propulsion pump
proportional solenoid valve or replace it if
necessary.
5. Neutral Solenoid
Valve
If spool of neutral solenoid valve is stuck,
pressure in both sides of servo cylinder
chamber is equalized. This causes
propulsion pump unable to discharge oil.
Measure pressure in servo cylinder
chambers. If pressure is equal in both
chambers, repair neutral solenoid valve or
replace it if necessary.
6. Suction Filter for
Steering • Charge
Pump
Steering • charge pump flow is reduced due
to clogged filter.
Clean suction filter or replace it if necessary.
7. Propulsion Circuit
Pressure
Pump does not discharge oil because
setting pressure of pressure cut off valve is
low.
Measure propulsion circuit pressure. If low,
check and adjust pressure cut off valve or
replace it if necessary.
Circuit does not obtain required pressure
because setting pressure of high pressure
relief is low.
Measure propulsion circuit pressure.
If low, check and adjust multifunction valve
or replace it if necessary.
•
•
8. Propulsion Motor Propulsion circuit pressure is not held in
propulsion motor case.
If pressure in propulsion motor case is not
within allowable range, repair propulsion
motor or replace it if necessary.
Internal leakage of propulsion motor. Measure drain quantity from propulsion
motor.
If drain quantity is larger than standard
value, repair propulsion motor or replace it
if necessary.
•
•
Sticking of brake discs causes brakes to
remain applied.
Replace brake discs.
•