JLG 1850SJ, Service And Maintenance Manual, Page: 390 / 712

SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
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5. Rotate the neutral adjusting screw clockwise half the
distance between the wrench positions noted above.
The gauges should read the same pressure, indicating
that the control is in its neutral position.
6. Hold the neutral adjusting screw stationary and tighten
the lock nut. Torque to 10.Nm [7 lbft]. Do not over
torque the nut.
7. When the neutral position is set, stop the prime mover,
remove the gauges, and install the gauge port plugs.
Reconnect the external control input.
NOTE: A small pressure differential of 1.5 bar [22 psi] or less is
acceptable. Zero differential is usually not possible.
MECHANICAL NEUTRAL ADJUSTMENT
Mechanical neutral is set with the pump running at 1800 min
(rpm). To set neutral, you must stroke the pump in each direc-
tion.
This procedure details setting neutral for the entire pump, one
side at a time. The procedure is the same for each side of each
pump so you will need to repeat it four times to set mechani-
cal neutral for both the front and rear sections. Alternate M4/
M5 and MA/MB to zero out forward and reverse directions of
the front unit, then move the gauges to M4/M5 of the rear unit
and MC/MD (system gauge ports for the rear unit). Refer to the
drawing that follows to identify all ports. The front and rear
sections are basically mirror images of each other. The control
solenoids C1 and C2 are marked on each control.
While performing this adjustment, you monitor the following
pressures.:
• Servo pressure at M4 and M5
• System pressure at MA and MB or MC and MD
• Pressure differential between M4 and M5 (optional)
• Pressure differential between A and B or C and D (optional)
PUMP SETUP
1. Attach a 50 bar [1000 psi] gauge to each servo pressure
port M4 and M5.
2. Attach a 600 bar [10 000 psi] gauge to each system pres-
sure port (MA and MB for front pump, MC and MD for
rear pump).
3. Remove servo cylinder locking screws (E350) and plates
(E300) from both sides of the pump.
4. Disconnect the control solenoids from the vehicle wir-
ing harness.
5. If using a PWM signal to set mechanical neutral, connect
the control solenoids C1 and C2 to the signal source.
Ensure the source supplies no current to the solenoids
until required in the following procedure.