TROUBLESHOOTING /SYSTEM PERFORMANCE

D-6. Bucket tilt-back motion is slow or tilt-back force is insufficient

Measure the bucket tilt-back time.

When a user complains that the bucket tilt-back motion is too sl ow, first measure the tilt-back time to determine whether the user feels the movement to be slowalthough the system is normal or it really moves too slowly due to malfun ction.

1. Measure the time required to move the bucket from maximum dum p (forward tilt) position to maximum tilt back (backward tilt) when the lift a rm is at the maximum height, in accordance with the description in the section of measurement of system performance.

Note: Values shown above are standard value for brand-new vehi cle. These values may be degraded when the vehicle has been used for c ertain period. Much longer than the standard Standard time Normal

（１）Too low fluid level in fluid tank

（２）Clogged suction strainer

（３）Excessive play in control linkage, poor adjustment

（４）Too low shovel main relief valve opening pressure or faulty main pump

（５）Faulty operation of priority valve

Troubleshooting

TROUBLESHOOTING /SYSTEM PERFORMANCE

D-6. Bucket tilt-back motion is slow or tilt-back force is insufficient

（１）Damaged tilt cylinder piston seals

C heck the tilt cylinder for internal leakage.

1. Lower the lift arm to the lowest position and tilt back the b ucket.

2. Disconnect the hose ① from the piston rod end (cylinder head) and close the disconnected end of the hose ① with the plug ② to prevent oil from spouting from the hose.

3. Start the engine and place the control lever in the "Tilt-bac k" position to apply oil pressure to the cylinder bottom end.

4. If oil flows out from the cylinder port ③, the cause can be determined to be damaged piston seals in the cylinder. Repair the tilt cylinder.

D-6. Bucket tilt-back motion is slow or tilt-back force is insufficient

（２） Too low overload relief valve opening pressure

Measurement of overload relief valve opening press ure

１． Connect an oil pressure gauge to the oil pressure check port ① of the tilt cylinder to measure the main relief valve opening pressure. Adjust the pressure if necessary according to the procedure below. Standard value of main pressure

２．Screw in the adjusting screw to increase the set pressure of the main relief valve ①. If the pressure does not rise w ith the adjusting screw turned down, the oil pressure gauge indicates the set pressure of the overload relief valve ② on the piston rod end.

First measure and adjust the set pressure of the overload relief valve, then adjust the set pressure of the main relie f valve ① to the standard value.

３．Lower the bucket flat on the ground, disconnect the tilt cylinder hoses ④ and ⑤ from the cylinder and interchange the hoses. (Connect the hose ④ to the cylinder bottom end and the hose ⑤ to the rod end.)

Caution: With the hoses connected as mentioned above, if the control lever is placed in the "Dump" position, t he bucket makes a "Tilt-back" motion; if the lever i s placed in the "Tilt-back" position, the bucket ma kes a "Dump" motion.

Screw in the adjusting screw to increase the set pressure of the main relief valve ① while holding the control lever in t he "Tilt-back" position (the bucket makes a "Dump" motion). When the pressure does not rise with the adjusting screw turned down, the oil pressure gauge indicates the set pressu re of the overload relief valve ③ on the cylinder bottom end.

First measure and adjust the set pressure of the overload relief valve, then adjust the set pressure of the main relief valve ① to the standard value. After these adjustments, interchange the tilt cylinder hoses ④ and ⑤ again to restore them to the original condition.

４．Standard set pressure for overload relief valves ② and ③

D-6. Bucket tilt-back motion is slow or tilt-back force is insufficient

5. If the measurements of the overload relief valve pressures in steps 1 to 3 are all the same and lower than the standard main relief valve opening pressure, the ca uses may be the following.

Faulty main relief valve Faulty main pump Faulty or poorly adjusted overload valves ② and ③

6. If the measurements of the overload relief valve opening pressure in steps 1 and 2 are the same, and they are lower than the standard main relief valve pressure, and the overload relief valve pressures measured in step 3 is equal to the standard pressure, then the c ause may be the following.

Faulty or poorly adjusted overload valve ②

＜Adjusting method＞

(1) Make preparations ready for an overload relief valve ② pressure measurement using an oil pressure gauge as described in step 2.

(2) Loosen the lock nut ⑥ of the overload relief valve ②.

(3) While reading the oil pressure gauge, turn the adjusting scr ew ⑦ with a hexagonal wrench so that the reading becomes equal to the standard pressure. Turn clockwise to raise the pressure. Turn counter-clockwise to lower the pressure Standard set pressure：２２．５ＭＰａ（２３０ｋｇｆ／ｃｍ2）

Caution: Never turn the adjusting screw quickly as the relief valve is very sensitive.

・Hold the adjusting screw ⑦ with a hexagonal wren ch when securing it with the lock nut ⑥.

・Measure the overload relief valve opening pressu re again to make sure that the pressure conforms to the standard pressure.

・Adjust the pressure of the main relief valve to the standard pressure.

D-6. Bucket tilt-back motion is slow or tilt-back force is insufficient

7. If the measurements of the overload relief valve opening pres sure in step 1 and 3 are the same, and they are lower than the standard main relief valve pressure, and the overload relief valve pressure measured in step 2 is equal to the stan dard pressure, then the cause may be the following.

Faulty or poorly adjusted overload valve ③

＜Adjusting method＞

(1) Make preparations ready for overload relief valve ③ pressure measurement using an oil pressure gauge as described in step 3.

(2) Loosen the lock nut ⑥ of the overload relief valve ③.

(3) While reading the oil pressure gauge, turn the adjusting screw ⑦ with a hexagonal wrench so that the reading becomes equal to the standard pressure.

Turn clockwise to raise the pressure. Turn counter-clockwise to lower the pressure. Standard set pressure

Caution: Never turn the adjusting screw quickly as the relief valve is very sensitive.

・Hold the adjusting screw ⑦ with a hexagonal wrench when securin g it with the lock nut ⑥.

・Measure the overload relief valve opening pressure again to mak e sure that the pressure conforms to the standard pressure.

・Adjust the set pressure of the main relief valve to the standard pressure.

（４）Restore the tilt cylinder hoses ④ and ⑤ to the original condition by interchanging their connection.

8. If the overload relief valve pressure measurement in step 2 i s higher than the standard pressure, adjust the overload relief valve ② in accordance with step 6.

9. If the overload relief valve pressure measurement in step 3 i s higher than the standard pressure, adjust the overload relief valve ③ in accordance with step 7.

Troubleshooting