JLG G6-42A Service Manual - Manual (Page 133)

8-5 G6-42A, G9-43A, G10-43A
Hydraulic System
8.3 HYDRAULIC PRESSURE DIAGNOSIS
JLG Parts Department has a kit available to use for
hydraulic system maintenance and troubleshooting: the
JLG Pressure Test Kit.
The hydraulic pressure test kit is used to pressure test the
various hydraulic components in the hydraulic system.
The kit includes:
• Gauges for testing high and low pressure circuits
• Fittings, couplers and hoses
• Durable carrying case
Contact local JLG Distributor for ordering information.
8.3.1 Pressure Checks and Adjustments
When diagnosing trouble in hydraulic system, use
hydraulic testing information in Section 8.4.1, “Hydraulic
Pressures.”
In general, follow steps below whenever conducting
pressure checks and performing adjustments:
1. Park machine on a firm, level surface. Engage park
brake, place travel select lever in (N) NEUTRAL,
level boom and turn engine OFF.
2. Test port is located at top right corner of main control
valve. Install a pressure gauge capable of measuring
at least 10% more pressure than that which circuit
being checked operates under.
3. Start engine. Operate machine 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 touch.
4. Refer to Section 8.4.1, “Hydraulic Pressures,” for
testing procedures.
5. Fully depress the accelerator pedal if required. Place
and hold the joystick in the position needed to
operate the particular machine function being
checked. Continue holding the joystick in position
until pressure readings are taken.
6. Check pressure gauge reading. It should read as
specified in Pressure Readings column of charts
found in Section 8.4, “Hydraulic Circuits.” If reading
is not as specified, turn engine OFF and check other
components in system. Verify that all related
hydraulic components and electrical switches,
sensors, solenoids, etc. are operating correctly.
7. Adjust relief valve by turning adjustment screw
clockwise will increase the pressure; turning screw
counterclockwise will decrease pressure.
8. Start engine and check pressure again. Turn engine
OFF. If there is pressure reading in gauge, bleed it
off then disconnect or remove pressure gauge from
the machine.
Part
Number
Description Approximate
Weight
Price and
Availability
70000652 Hydraulic Pressure Test
Kit
10 lbs. Consult Factory
70000101 Digital Hydraulic
Pressure Test Kit
7 lbs. Consult Factory