SECTION 4 - HYDRAULICS
3121642 – JLG Lift – 4-25
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 CONTAMINA-
TION.
KEEP IT CLEAN
Clean the outside of the pump thoroughly before disassembly.
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. PROTECT ALL EXPOSED SEALING SUR-
FACES AND CAVITIES FROM DAMAGE AND FOREIGN MATERIAL. IF LEFT UNAT-
TENDED, COVER THE PUMP WITH A PROTECTIVE LAYER OF PLASTIC.
REPLACE ALL O-RINGS & GASKETS
Replace all o-rings and seals during service. Lightly lubricate 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 installa-
tion 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 efficiency 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 com-
ponents (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 filter.
Fill inlet line from reservoir to pump. Ensure construc-
tion 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 DURING START-UP.
AIR ENTRAPMENT IN OIL UNDER HIGH PRESSURE MAY DAMAGE 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.
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