JLG 1350SJP Service Manual - Manual (Page 360)

SECTION 5 - HYDRAULICS
5-36 – JLG Lift – 3121142
NOTE: Shim thickness 1 mm = 56 psi (3.86 bar). Shims are avail-
able in 0.3, 0.5, and 1.0 mm thickness.
Mechanical Centering of Pump
PREPARATION FOR ADJUSTMENT
The control piston has strong centering springs to ensure that
once the pump is adjusted for the neutral position it will
always return to neutral. If an adjustment is necessary follow
the steps listed below.
To ensure there is equal pressure on both sides of the control
module during the centering operation, it is necessary to con-
nect the X
1
and X
2
ports together by means of hose or tubing.
(No less than a 1/4 inch ID) The port sizes are:
With pressure gages installed at M
A
, and M
B
, and with A and B
ports blocked (or motor stalled), and with the pump running,
loosen the jam nut. Turn the mechanical centering adjusting
screw until 1000 psi is read on M
A
, or M
B
then turn screw
opposite direction until 1000 psi is read on other pressure
port. Turn the screw back, splitting the distance between the
previous two positions. This should be the neutral position.
Pressure on M
A
, and M
B
should be equal.
Tighten jam nut, stop the pump drive, remove the hose con-
necting ports X
1
and X
2
.
Hydraulic Centering of Control Modules
PREPARATION FOR ADJUSTMENT
When control modules are exchanged or replaced, it is gener-
ally necessary to center the new module. This is done by run-
ning the pump with gauges installed at ports X
1
, X
2
, M
A
, and
M
B
Release the jam nut and turn the adjustment screw on top
of the control module valve body.
The adjustment screw is an eccentric, therefore, turning more
than 90’ in either direction will have no further centering
effect, and could cause damage to the eccentric pin.
CENTERING THE EP CONTROL MODULE
With no electrical signal to solenoids A and B, (remove both
plug-in connectors), the EP control module is correctly
adjusted when any or all of the following conditions exist:
1. Approximately, when equal control pressures are
obtained at control pressure ports X
1
and X
2
.
2. The hydraulic motor does not turn when the brake is
released.
3. Charge pressure is registered equally at ports M
A
and
M
B
, when the flow output of the pump is deadheaded
against a locked motor or a valve.
If difficulties are encountered in obtaining neutral position of
the HD or EP control modules, check that the ends of the con-
Pump Size Allen Wrench Wrench
28 5 mm 17 mm
Pump Size Tool Required Wrench
28 Screwdriver 10 mm