Vehicle Systems
Testing and Adjusting
46
Problem: The load lowers when the lift spool is
moved from the NEUTRAL position to the RAISE
position.
Probable Cause:
1.
There is foreign material in the load check valve
area.
2.
The load check valve and seat show wear.
3.
Sudden loss of pump oil pressure.
4.
Damage to the relief valve which causes low oil
pressure.
Problem: Spool do not return to neutral.
Probable Cause:
1.
The springs are broken.
2.
The spool is bent.
3.
The system valve has foreign particles in it.
4.
The control linkage is not in alignment.
5.
The fastening bolts of the valve have too much
torque.
Problem: No motion or slow, then a too sudden
action of the hydraulic system.
Probable Cause:
1.
The relief valve is not correctly set, or will not
move in base and/or is worn.
2.
There is air in the system.
3.
Dirt or foreign particles between relief valve
control poppet and its seat.
4.
Valve body has a crack inside.
5.
Spool not moved to a full stroke.
Lift and Tilt Cylinders
Problem: Leakage around the piston rod.
Probable Cause:
1.
Cylinder head (bearing) seals are worn.
2.
Piston rod is worn, scratched or bent.
Problem: There is leakage of oil inside the
cylinder or loss of lift or tilt power.
Probable Cause:
1.
The piston seals are worn and let oil go through.
2.
Cylinder has damage.
Problem: The piston rods show wear.
Probable Cause:
1.
The cylinders are not in correct alignment.
2.
Oil is dirty.
Problem: Foreign material behind the wiper
rings causing scratches on the cylinder rod.
Probable Cause:
1.
The wiper rings show wear and do not remove
dirt and foreign material.
