TROUBLESHOOTING /SYSTEM PERFORMANCE

A-2. Machine can be moved only in forward or reverse direction

（２）Faulty operation of forward or reverse solenoid valve

Perform operation check of the solenoid valve（YUKEN)

1. Insert and push a long, round stick B into the hole A(inside diameter: 6 mm) in the solenoid valve.

2. The solenoid valve is normal if reaction force of the spring D is felt and the piston C moves inward by 2.8 mm and it returns smoothly on release of the force on the stick.

Faulty Normal

Replace the solenoid valve.

Troubleshooting

TROUBLESHOOTING /SYSTEM PERFORMANCE

A-2. Machine can be moved only in forward or reverse direction

（３）Measurement of high-pressure circuit pressure（YUKEN）

Measure the high-pressure circuit pressure of the HST pump.

1. Connect an oil pressure gauge to the port A ("forward").

2. Measure the oil pressure in the high-pressure circuit in accordance with the descriptions in the measurements of performance.

3. Refer Performance standard list for standard value.

Lower pressure than standard value

Standard value

Faulty high-pressure relief valve Inspect the HST motor.

Troubleshooting

TROUBLESHOOTING /SYSTEM PERFORMANCE

A-2. Machine can be moved only in forward or reverse direction

（３）Measurement of high-pressure circuit pressure（UCHIDA）

Measure the high-pressure circuit pressure of the HST pum p.

1. Connect an oil pressure gauge to the port MA ("forward").

2. Measure the oil pressure in the high-pressure circuit in accordance with the descriptions in the measurements of performance.

3. Refer Performance standard list for standard value.

Lower pressure than standard value

Standard value

Faulty high-pressure relief valve

Inspect the HST motor.

Troubleshooting

TROUBLESHOOTING /SYSTEM PERFORMANCE

A-2. Machine can be moved only in forward or reverse direction

（４）Faulty high-pressure relief valve

Remove and check the high-pressure relief valve.

1. Check the high-pressure relief valves for looseness or other defects in installation. (If a valve is loose, the fluid in high-pressure circuit leak s into low-pressure circuit resulting in a drop in the high-pressure circuit pressure.)

2. If no defect is found in the installation, remove the high-pr essure relief valve and check the valve for presence of foreign matter on the valve s eats ① and ②.

3. Interchange the "forward" and "reverse" high-pressure relief valves and check whether the abnormal condition change.

4. Replace the high-pressure relief valves with new ones, and ch eck whether the abnormal condition recurs.

Troubleshooting