SECTION 4 - HYDRAULICS
3121642 – JLG Lift – 4-9
31. If applicable, install the cartridge-type holding valve and
fittings in the port block using new o-rings as applica-
ble. Refer to Table 4-2, Holding Valve Torque Specifica-
tions.
4.6 DRIVE PUMP START-UP PROCEDURE
THE FOLLOWING PROCEDURE SHOULD ALWAYS BE PERFORMED WHEN START-
ING A NEW PUMP OR WHEN RESTARTING AN INSTALLATION IN WHICH EITHER
THE PUMP OR MOTOR HAVE BEEN REMOVED FROM THE SYSTEM.
THE FOLLOWING PROCEDURE SHOULD ALWAYS BE PERFORMED WHEN START-
ING A NEW PUMP OR WHEN RESTARTING AN INSTALLATION IN WHICH EITHER
THE PUMP OR MOTOR HAVE BEEN REMOVED FROM THE SYSTEM.
THE FOLLOWING PROCEDURE MAY REQUIRE THE MACHINE TO BE DISABLED
(WHEELS RAISED OFF THE GROUND, DRIVE FUNCTION DISCONNECTED, ETC.)
WHILE PERFORMING THE PROCEDURE IN ORDER TO PREVENT INJURY TO
TECHNICIAN AND OTHER PERSONNEL. TAKE NECESSARY SAFETY PRECAU-
TIONS BEFORE MOVING THE MACHINE.
Prior to installing pump and/or motor, inspect unit(s) for dam-
age incurred during shipping and handling. Make certain all
system components (reservoir, hoses, valves, fittings, heat
exchanger, etc.) are clean prior to filling with hydraulic fluid.
Fill reservoir with recommended hydraulic fluid, which should
be passed through a 10 micron (nominal, no bypass) filter
prior to entering the reservoir. The use of contaminated fluid
will cause damage to components, which may result in unex-
pected machine movement.
The inlet line leading from the reservoir to the pump should
be filled prior to start-up. Check inlet line for properly tight-
ened fittings and make sure it is free of restrictions and air
leaks.
Be certain to fill pump and/or motor housing with clean
hydraulic fluid prior to start-up. Fill housing by pouring filtered
oil into upper case drain port.
Install a 0 to 500 psi (0 to 35 bar) pressure gauge in the charge
pressure gauge port to monitor charge pressure during start-
up.
It is recommended that the external control input signal elec-
trical connections be disconnected at the pump control until
after initial start-up. This will allow the pump to remain in its
neutral position.
“Jog” or slowly rotate prime mover until charge pressure starts
to rise. Start prime mover and run at the lowest possible RPM
until charge pressure has been established. Excess air may be
bled from high pressure lines through high pressure gauge
ports.
DO NOT START PRIME MOVER UNLESS PUMP IS IN NEUTRAL POSITION (0
DEGREES SWASHPLATE ANGLE). TAKE PRECAUTIONS TO PREVENT MACHINE
MOVEMENT IN CASE PUMP IS ACTUATED DURING INITIAL START-UP.
Once charge pressure has been established, increase speed to
normal operating RPM. Charge pressure should be approxi-
mately 220 psi (15.5 bar) minimum. If charge pressure is incor-
rect, shut down and determine cause for improper pressure.
INADEQUATE CHARGE PRESSURE WILL AFFECT THE OPERATOR’S ABILITY TO
CONTROL THE MACHINE.
Shut down prime mover and connect external control input
signal. Start prime mover, checking to ensure pump remains in
neutral. With prime mover at normal operating speed, slowly
check for forward and reverse machine operation.
Charge pressure should remain at 220 psi to 240 psi (15.5 bar
to 16.9 bar) minimum during forward or reverse operation.
Continue to cycle slowly between forward and reverse for at
least five minutes.
Shut down prime mover, remove gauges, and plug ports.
Check reservoir level and add fluid if necessary.
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