JLG 4394RT Service Manual - Manual (Page 190)

SECTION 4 - HYDRAULICS
4-24 – JLG Lift – 3121249
General Repair Instructions
REMOVAL:
PRIOR TO PERFORMING REPAIRS, REMOVE THE UNIT FROM
THE MACHINE. CHOCK WHEELS ON THE MACHINE TO INHIBIT
MOVEMENT. BE AWARE THAT HYDRAULIC FLUID MAY BE
UNDER HIGH PRESSURE AND/OR HOT. INSPECT THE OUTSIDE
OF THE PUMP AND FITTINGS FOR DAMAGE. CAP HOSES AFTER
REMOVAL TO PREVENT CONTAMINATION.
KEEP IT CLEAN
Clean the outside of the pump thoroughly before disas-
sembly. Take care not to contaminate system ports. Clean
parts using a clean solvent wash and air dry.
AS WITH ANY PRECISION EQUIPMENT, YOU MUST KEEP ALL
PARTS FREE OF FOREIGN MATERIAL AND CHEMICALS. PRO-
TECT ALL EXPOSED SEALING SURFACES AND CAVITIES FROM
DAMAGE AND FOREIGN MATERIAL. IF LEFT UNATTENDED,
COVER THE PUMP WITH A PROTECTIVE LAYER OF PLASTIC.
REPLACE ALL O-RINGS & GASKETS
Replace all o-rings and seals during service. Lightly lubri-
cate o-rings with clean petroleum jelly prior to assembly.
SECURE THE UNIT
Place the unit in a stable position with the shaft pointing
downward. It will be necessary to secure the pump while
removing and torquing fasteners and components.
PERFORMING MINOR REPAIRS ACCORDING TO THIS SECTION
WILL NOT AFFECT THE PUMP’S WARRANTY. MAJOR REPAIRS
REQUIRING THE REMOVAL OF THE UNIT’S CENTER SECTION,
SERVO SLEEVES, OR FRONT FLANGE VOIDS WARRANTY.
Start-Up Procedure
Follow this procedure when starting-up a new pump
installation or when restarting an installation in which the
pump has been removed and re-installed on the
machine. Ensure pump has been thoroughly tested on a
test stand before installing on a machine.
These pumps should never be dry started. The time it
takes for the charge pump to create a vacuum to draw in
the fluid, send it out through the charge pump filter and
then back in to the pump may take 30-40 seconds. During
this time the surface between the cylinder barel and valve
plate are running dry. This can afec the volumetric effi-
ciency of the pump and cause premature failure of the
pump. Pre-filling the case also reduces the time it takes fro
the pump to create a vacuum to draw fluid into the pump.
TO PROTECT AGAINST UNINTENDED MOVEMENT, SECURE THE
MACHINE OR DISABLE/DISCONNECT THE MECHANISM WHILE
SERVICING.
NOTE: Prior to installing the pump, inspect for damage that
may have occurred during shipping.
1. Ensure that the machine hydraulic oil and system
components (reservoir, hoses, valves, fittings, and
heat exchanger) are clean and free of any foreign
material.
2. Install new system filter element(s) if necessary.
Check that inlet line fittings are properly tightened
and there are no air leaks.
3. Install the pump. Install a 1000 psi (50 bar) gauge in
the charge pressure gauge port M3.
4. Fill the housing by adding filtered oil in the upper
case drain port. If the control is installed on top,
open the construction plug in the top of the control
to assist in air bleed.
5. Fill the reservoir with hydraulic fluid of the recom-
mended type and viscosity. Use a 10-micron filler fil-
ter. Fill inlet line from reservoir to pump. Ensure
construction plug in control is closed after filling.
6. Disconnect the pump from all control input signals.
7. Close construction plug removed in step 4.
AFTER START-UP, THE FLUID LEVEL IN THE RESERVOIR MAY
DROP DUE TO SYSTEM COMPONENTS FILLING. DAMAGE TO
HYDRAULIC COMPONENTS MAY OCCUR IF THE FLUID SUPPLY
RUNS OUT. ENSURE RESERVOIR REMAINS FULL OF FLUID DUR-
ING START-UP.
AIR ENTRAPMENT IN OIL UNDER HIGH PRESSURE MAY DAM-