JLG 4394RT Service Manual - Manual (Page 191)

SECTION 4 - HYDRAULICS
3121249 – JLG Lift – 4-25
AGE HYDRAULIC COMPONENTS. CHECK CAREFULLY FOR
INLET LINE LEAKS.
DO NOT RUN AT MAXIMUM PRESSURE UNTIL SYSTEM IS FREE
OF AIR AND FLUID HAS BEEN THOROUGHLY FILTERED.
8. Disable the engine to prevent it from starting. Crank
the starter for several seconds. Do not exceed the
engine manufacturer’s recommendation. Wait 30
seconds and then crank the engine a second time
as stated above. This operation helps remove air
from the system lines. Refill the reservoir to recom-
mended full oil level.
9. When the gauge begins to register charge pressure,
enable and start engine. Let the engine run for a
minimum of 30 seconds at low idle to allow the air to
work itself out of the system. Check for leaks at all
line connections and listen for cavitation. Check for
proper fluid level in reservoir.
10. When adequate charge pressure is established (as
shown in model code), increase engine speed to
normal operating rpm to further purge residual air
from the system.
11. Shut off engine. Connect pump control signal. Start
engine, checking to be certain pump remains in
neutral. Run engine at normal operating speed and
carefully check for forward and reverse control oper-
ation.
12. Continue to cycle between forward and reverse for
at least five minutes to bleed all air and flush system
contaminants out of loop.
NOTE: Normal charge pressure fluctuation may occur dur-
ing forward and reverse operation.
13. Check that the reservoir is full. Remove charge pres-
sure gauge. The pump is now ready for operation.
Removing the pump
CONTAMINATION CAN DAMAGE INTERNAL COMPONENTS AND
VOID THE MANUFACTURER’S WARRANTY.
TAKE PRECAUTIONS TO ENSURE SYSTEM CLEANLINESS WHEN
REMOVING AND INSTALLING SYSTEM LINES.
DISASSEMBLY:
1. With the prime mover off, thoroughly clean all dirt
and grime from the outside of the pump.
2. Tag, disconnect, and cap each hydraulic line con-
nected to the pump. As hydraulic lines are discon-
nected, plug each open port, to ensure that dirt and
contamination do not get into the pump.
3. Remove the pump and its auxiliary pump (if applica-
ble) as a single unit.
NOTE: Be careful, do not damage solenoids and electrical
connections when using straps or chains to support
the pump.
INSPECTION:
4. Ensure the work surface and surrounding area are
clean and free of contaminants such as dirt and
grime.
5. Inspect the system for contamination.
6. Look at the hydraulic fluid for signs of system con-
tamination, oil discoloration, foam in the oil, sludge,
or metal particles.
REASSEMBLY:
7. Before replacing the pump, replace all filters and
drain the hydraulic system. Flush the system lines
and fill the reservoir with the correct, filtered hydrau-
lic fluid.
8. Fill the pump with clean, filtered hydraulic fluid.
9. Attach the pump to the prime mover. Torque mount-
ing screws according to the manufacturers recom-
mendation.
10. Replace all hydraulic lines. Ensure the charge inlet
line is filled with fluid.