Specifications

Vehicle System Testing & Adjusting 50
Problem: The carriage will not lower correctly.
Probable Hydraulic Cause:
1. The electric switch (on-off) below a seat got
damaged.
2. The electric parts (relay and controller) related to
a solenoid valve in lift section of control valve got
failed.
Probable Mechanical Cause:
1.Lift poppet (lift lock) damaged and contaminated.
2. Needle valve is loosened.
Problem: The lift or tilt cylinders do not hold their
position with the valve control levers in neutral
position.
Probable Cause:
1. The valve spools do not hold their positions
because the springs for the valve spools are
weak or broken.
2. Control valve leakage caused by worn valve
spools or seals.
3. The check valves in the control valve are
defective.
4. Leakage of the cylinder lines or piston seals.
5. There is foreign material in the control valve.
Hydraulic Pump
Problem: Noise in the pump.
Probable Cause:
1. The oil level is low.
2. The oil is thick (viscosity too high) or seals..
3. The pump inlet line has a restriction in it (strainer
plugged).
4. Worn parts in the pump.
5. Oil is dirty.
6. Air leaks into the inlet line.
Problem: The oil temperature is too high.
Probable Cause:
1. The oil level is low.
2. There is a restriction in an oil passage.
3. The relief valve setting is too low.
4. The oil is too thin.
5. There is air leakage in the system.
6. The pump has too much wear.
7. The system operates at too high a pressure.
a. Relief valve setting too high.
b. Attachment components cause a restriction
during movement.
c. Restrictions in flow control valve, load check
valve and in oil lines.
8. Severe hydraulic usage.
Safety lift lock function: Once the operator
leaves a seat more than 3 seconds or a start
key is off, the lift cylinder doesn’t lower even
though lift lever is pulled for lowering. If the
operator is seated or, a key is on, the lowering
will normall
y
wor
k
immediatel
y
.