Pressure Checks And Adjustments - JLG sky trak mmv Service Manual

Hydraulic System
9.6.1

Pressure Checks and Adjustments

When diagnosing trouble in the hydraulic system, use the
hydraulic testing information in Section 9.7, Hydraulic
System Testing .
In general, follow the steps below whenever conducting
pressure checks and performing adjustments:
1. Park the vehicle on a firm, level surface. Engage the
park brake, place the travel select lever in [N]
NEUTRAL, place the neutral lock lever in the [N]
NEUTRAL LOCK position, level the boom and turn
the engine OFF.
2. Pressure tee fittings are conveniently located in each
hydraulic circuit. Install a pressure gauge capable of
measuring at least 10% more pressure than that
which the circuit being checked operates under.
WARNING:
operation in closed areas with inadequate ven-
tilation. Failure to properly ventilate exhaust
fumes can result in death or serious injury.
3. Start the engine. Operate vehicle functions several
times to allow hydraulic oil to reach operating
temperature. The hydraulic oil temperature should
be between 100-120° F (38-49° C). If a temperature
gauge or thermometer is unavailable, the hydraulic oil
reservoir should be warm to the touch.
9.8
Avoid prolonged engine
4. Refer to Section 9.7, Hydraulic System Testing for
testing procedures.
5. Fully depress the accelerator pedal as required.
Place and hold the joystick in the position needed to
operate the particular vehicle function being
checked. Continue holding the joystick in position
until pressure readings are taken.
6. Check the pressure gauge reading. It should read as
specified in the Pressure Readings column of the
charts found in Section 9.7, Hydraulic System
Testing . If the reading is not as specified, turn the
engine OFF and check other components in the
system. Verify that all related hydraulic components
and electrical switches, sensors, solenoids, etc. are
operating correctly.
7. As a last resort, adjust the appropriate relief valve, if
applicable. Turning the adjustment screw clockwise
will increase the pressure; turning the screw
counterclockwise will decrease the pressure.
WARNING:
operation in closed areas with inadequate ven-
tilation. Failure to properly ventilate exhaust
fumes can result in death or serious injury.
8. Start the engine and check the pressure again. Turn
the engine OFF, then disconnect or remove the
pressure gauge from the vehicle.
Avoid prolonged engine
Model MMV Rev. 12/04