JLG G5-18A Service Manual - Manual (Page 80)

Hydraulic System
8.6 G5-18A/2505
8.5.2 Main Control Valve Pressure Checking
Attach 5000 psi (345 bar) gauge to the test port (1) at the
rear of the implement pump to check the system
pressure. Make sure the gauge is visible from inside the
cab.
See Section 8.5.1, “Pressure Checks and Adjustments,”
for start up procedure. Check the main control pressure
with the park brake on and the service brake off at full
throttle. Retract a boom circuit function until the cylinder
bottoms. The main control valve pressure should be 3625
±50 psi (250 ±4 bar) at full throttle. Repeat for each boom
circuit to verify the correct main control valve pressure.
If a pressure adjustment is required, adjust the main relief
cartridge (2) on the main control valve. Recheck pressure
after any adjustment has been made.
8.5.3 Charge Pressure Checking
Attach a pressure gauge to the test port (3) on the
hydrostatic transmission to check the system pressure.
The pressure should be 360 +50 psi (25 + 4 bar) with the
engine at idle.
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.
8.5.4 Boom Function Pressure Checking
Attach 5000 psi (345 bar) gauge to the test port (1) at the
rear of the implement pump to check the system
pressure. Make sure the gauge is visible from inside the
cab.
See Section 8.5.1, “Pressure Checks and Adjustments,”
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 3625 ±50 psi (250 ±4 bar) at full throttle.
Note: With the machine at operating temperature, the
3625± 50 psi (250 bar) pressure reading at the main
control valve is 125 psi (13,3 bar) HIGHER than the 3500
± 50 psi (241 bar) of each individual valve section
function. DO NOT adjust the main control valve relief
pressure below 3625 ± 50 psi (250 bar).
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.
MY2540
1
MY2110
2
MY1930 4
3