JLG 723A Service Manual - Manual (Page 88)

Hydraulic System
8-6 L2906H, 2906H, 3507H, 619A, 723A, 29.6LP, 29.6, 35.7
8.6.3 Charge Pressure Checking
Attach a pressure gauge to the test port (3) on the
hydrostatic transmission (4) to check the system
pressure. The pressure should be 26,2 ± 2 bar
(380 ± 30 psi) with the engine at low idle.
The charge pressure relief valve is preset at the factory
and is not adjustable.
8.6.4 Drive Pressure Checking
Attach a pressure gauge to the test fitting (5) on the
hydrostatic transmission (4) to check the system
pressure.
The following procedure must be performed to verify
proper drive pressure:
• Connect a JLG handheld analyzer to the power
distribution board (located below the rear cab
window).
• Enter service code 01769 for access level 1.
• Navigate to CALIBRATION>TRACTION TEST,
select YES. (Note: this mode will return to the default
setting NO when the power is cycled.)
• Check the drive pressure with the park brake on,
wheels chocked and the service brake off at full
throttle. The pressure reading should be 440 to 460
bar (6381 to 6671 psi).
Do NOT adjust any relief settings. The unit is preset at the
factory and should not be tampered with. If the proper
pressure is not read, the unit may be defective.
8.6.5 Boom Function Pressure Checking
Attach 345 bar (5000 psi) gauge to the test port (6) at the
rear of the main control valve to check the system
pressure. Make sure the gauge is visible from inside the
cab.
See Section 8.6, “Hydraulic Pressure Diagnosis,” for start
up procedure. Check the boom function pressure with the
park brake on and the service brake off at full throttle.
Retract each boom circuit function until the cylinder
bottoms. Each circuit function pressure should be
250 ± 2,8 bar (3625 ± 40 psi) at full throttle.
Note: With the machine at operating temperature, the
250 ± 2,8 bar (3625 ± 40 psi) pressure reading at the
main control valve is 13,3 bar (125 psi) HIGHER than the
241 bar ±4 bar (3500 ± 50 psi) of each individual valve
section function. DO NOT adjust the main control valve
relief pressure below 250 ± 2,8 bar (3625 ± 40 psi).
To check individual valve section pressures, install a tee
and test port between the cylinder being checked and
the corresponding valve section on the main control
valve.
The individual valve section relief valves are preset at the
factory and are not adjustable.
MZ5520
4
3
5
MZ5500
6
7