Lull 944E-42, Service Manual

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8.91 Model 644E-42/944E-42 Rev. 6/04
Hydraulic System
Refer to Section 10.3, “Stabil-TRAK™
Operation,” for information on
troubleshooting the frame sway and
stabilizer circuits.
NOTE:
When checking pressures in
circuits, refer to Section 8.7,
“Hydraulic System Testing,” for
correct pressure readings.
Not
OK
Not
OK
With the boom below 40°, if
the frame sway cylinder will
not sway left, drifts or reacts
slowly, check pilot line
connections at the main
control valve.
Replace check valves on
frame sway cylinder.
If OK
If OK
Not
OK
Inspect pilot-operated check
valves on frame sway
cylinder.
Repair/tighten connections.
Ensure frame sway section of
main control valve is
functioning.
Check orifice in check valve
fittings.
Clean/replace orifice fittings.
NOTE:
Refer to Section 2.5.6, “Hydraulic Cylinder
Performance Specifications,” for approximate
cylinder cycle times. The operation of the system
function should approximate the times listed.
If OK
Not
OK
Check frame sway cylinder
seals.
Repair/replace frame sway
cylinder.
Before troubleshooting any
hydraulic circuit, ALWAYS
begin by checking the
following:
1. Hydraulic oil level in the
reservoir
2. All hoses, tubes, fittings
for leaks, kinks,
interference, etc.
3. Air in the lines