Lull 944E-42 Service Manual - Manual (Page 355)

8.103 Model 644E-42/944E-42 Rev. 6/04
Hydraulic System
NOTE:
When checking pressures in
circuits, refer to Section 8.7,
“Hydraulic System Testing,” for
correct pressure readings.
If the attachment tilt
cylinder extends slowly.
Not
OK
Isolate and check each slave
cylinder for seal leaks.
Repair/replace
slave cylinder(s).
Not
OK
Check pilot pressure at “PPG”
port of accumulator charge/
secondary function valve.
Adjust/repair/replace
pressure reducing cartridge
on accumulator charge/
secondary function valve.
Not
OK
Check counterbalance valve
on attachment tilt cylinder.
Replace the
counterbalance valve.
Not
OK
Check pilot operated check
valve on attachment tilt
cylinder.
Replace the pilot operated
check valve.
Not
OK
Check port relief at main
control valve
Replace the relief valve on
attachment tilt section of main
control valve.
Not
OK
Check seals in
attachment tilt cylinder.
Repair/replace
attachment tilt cylinder.
Not
OK
Inspect pump. Refer to
Hydraulic Testing
pages 8.12 through 8.54.
Check the cycle times for
boom LIFT and boom
EXTEND to determine pump
performance. Pump flow
directly controls these cycle
times. Refer to Section 2.5.6,
“Hydraulic Cylinder
Performance Specifications,”
for correct cycle times.
If OK
If OK
If OK
If OK
If OK
If OK
Not
OK
Replace counterbalance and/
or pilot-operated check valves
on the attachment tilt cylinder.
Check counterbalance and
pilot-operated check valves.
Not
OK
Check seals in attachment
slave cylinder.
Repair/replace slave cylinder.
If OK
Not
OK
If the attachment tilt
cylinder drifts or reacts
slowly, check the seals on
the attachment tilt cylinder.
Repair/replace attachment
tilt cylinder.
If OK
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