Removing The Pump; Inspection; Replacement - JLG 1850SJ Service And Maintenance Manual

SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
SERVO ADJUSTMENT
6. Run prime mover at 1800 min (rpm).
7. If using a PWM signal, ensure the signal is off. Check the
servo pressure gauges. Ensure the differential between
M4 and M5 is less than 1.5 bar [22 psi].
8. Using a 3/4 in deep socket, unthread both servo cylin-
ders 2-3 turns. This step ensures the servo cylinders have
no contact with the servo piston.
9. Stroke the pump by turning the control eccentric screw
(or supplying current to solenoid C1) until the servo
pressure at port M4 is 1 to 2 bar [14 -29 psi] greater than
at port M5 and the system pressure gauges indicate dis-
placement. Pressure should be greater at port MA for
clockwise rotation, or MB for counterclockwise rotation.
This also indicates the servo piston is in contact with the
servo cylinder on side M5.
10. Slowly thread the servo cylinder on the M5 side in until
the system pressure differential starts to decrease. Main-
tain servo pressure differential between 1-2 bar [14-29
psi] during this step. Continue turning the servo cylinder
in until the system pressure differential (between ports
MA/MB or MC/MD) is less than 1.5 bar [22 psi]. This pro-
cedure sets the servo and swashplate to mechanical
neutral on the M5 side.
11. To complete setting neutral, repeat steps 1-5 but stroke
the pump in the opposite direction by turning the
eccentric screw in the opposite direction, or by supply-
ing current to solenoid C2. Reverse gauge locations (M4
for M5, MB for MA etc.) from those stated above since
the pump is now stroking the other direction.
12. Set neutral for the rear pump by repeating steps 1-6 on
the rear pump. Remember that the rear pump is a mirror
image of the front pump and therefore the locations of
the servo gauge ports (M4/M5) and the control sole-
noids (C1/C2) are opposite.
13. Remove all gauges and replace gauge port plugs.
5-140

Removing The Pump

Before working on the pump, thoroughly clean the outside. If
the pump has an auxiliary pump attached, remove both
pumps as a single unit. Tag and cap all hydraulic lines as you
disconnect them, and plug all open ports to ensure that dirt
and contamination do not get into the system.
CONTAMINATION CAN DAMAGE INTERNAL COMPONENTS. TAKE PRECAU-
TIONS TO ENSURE SYSTEM CLEANLINESS WHEN REMOVING AND INSTALL-
ING SYSTEM LINES.
1. Thoroughly clean all dirt and grime from the outside of
the pump.
2. Tag, disconnect, and cap each hydraulic line connected
to the pump. As hydraulic lines are disconnected, 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 applicable)
as a single unit.
NOTE: Be careful, do not damage solenoids and electrical connec-
tions when using straps or chains to support the pump.

Inspection

1. Ensure the work surface and surrounding area are clean
and free of contaminants such as dirt and grime.
2. Inspect the system for contamination.
3. Look at the hydraulic fluid for signs of system contami-
nation, oil discoloration, foam in the oil, sludge, or metal
particles.

Replacement

1. Before replacing the pump, replace all filters and drain
the hydraulic system. Flush the system lines and fill the
reservoir with the correct, filtered hydraulic fluid.
2. Fill the pump with clean, filtered hydraulic fluid.
3. Attach the pump to the prime mover. Torque mounting
screws according to the manufacturers recommenda-
tion.
4. Replace all hydraulic lines. Ensure the charge inlet line is
filled with fluid.
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