Vehicle Systems Hydraulic System Operation
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Lift Section
• The lift section has a single work port to direct flow to the lift cylinder is single-acting (gravity returns the
mast to the lowered position).
• The lift section also contains part of the components which comprise the ISO safety features. There is a
normally closed solenoid valve that works in conjunction with a lift lock check valve. When the operator is
not seated, the solenoid valve is not energized, which ensures that pressures are equalized across the lift
lock valve closed and prevents lowering of the mast.
• Lifting: When the operator shifts the lever backwards, the spool is extended out of the valve and this opens
the internal fluid passages that lift the mast. Oil flows through the high pressure parallel cavity, past the
load check valve, through the spool metering notches, past the lift lock check valve, and to the head side of
the lift cylinder.
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