JLG sky trak mmv Service Manual page 309

Engine Information
Idle. . . . . . . . . . . . . . . . . . . . . . . . 1,050 ±50 rpm
Full Speed . . . . . . . . . . . . . . . . . 2,750 ±100 rpm
Hydraulic Oil Information
Oil Type - Meets MIL-PRF-2104G Specifications
Capacity - Reservoir . . . . . . 28.5 gal. (108 liter)
Capacity - System . . . . . . . . 41.3 gal. (156 liter)
Note: To adjust relief settings, pressure reducing settings
or standby pressure, turn the adjustment screw clockwise
to increase pressure or counterclockwise to decrease
pressure.
The hydraulic oil temperature for the pump flow test should
be between 100-120° F (38-49° C) (tank hot to the touch)
during testing.
TEST
LOCATION
To check flow readings a flow meter capable of measuring 60 gpm (227 ltr/min) and a load valve capable of
6,000 psi (413,4 bar) will be required (not included with Hydraulic Diagnostic Test Kit).
1
Test both pumps separately. When testing the pumps, return the oil from the flow meter directly into the tank fill.
2,000 psi (137,8 bar) load @ Engine Speed of 2,500 ±25 rpm — Flow rate should be 16.5-19.5 GPM (62,5-73,8 ltr/min).
TEST ADJUST.
LOCATION LOCATION
2a
2
2b
2
N/A
2
N/A
3
4 3a
N/A
5
4a
6
N/A
6
N/A
7
8 5a
N/A
9
N/A
10
6a
11
Model MMV Rev. 12/04
2
5
COMPONENT PRESSURE
DESCRIPTION READINGS
Unloader Valve Main System Relief
3,500 ±100 psi
(241 ±6,9 bar)
Main Control Valve Extend/Retract Base
3,200 ±100 psi
(220,6 ±6,9 bar)
Attachment Tilt Relief/ 3,500 ±100 psi
FORWARD or (241 ±6,9 bar)
REARWARD
Unloader Valve Load Sense
3300 +200/-100 psi
(227 +14/-7 bar)
Accumulator Charge Steering Relief
Valve 2,500 ±100 psi
(172,3 ±7 bar)
Secondary Function Park Brake Release
Manifold 550 ±100 psi
(37,9 ±7 bar)
Secondary Function Pilot Pressure
Manifold 550 ±100 psi
(37,9 ±7 bar)
Brake Valve 600 ±50 psi
(Manual Brake Pressure) (41,4 ±3,4 bar)
Brake Valve 600 ±50 psi
(Service Brake Pressure) (41,4 ±3,4 bar)
Stabilizer Cylinder
(5,2-10,3 bar)
Accumulator Charge Load Sense
Valve 0-2600 psi (0-179 bar)
Accumulator Charge See "Pressure Test
Valve Procedures" for
Pressure Readings
Unloader Valve Standby Pressure
200 ±50 psi
(13,8 ±3,4 bar)
Equipment Needed To Perform Tests
From Hydraulic Diagnostic Test Kit
Circuit Gauge
5,000 psi gauge
4 (345 bar)
3
9 10
2,000 psi gauge
6
7 (138 bar)
300 psi gauge
8 11
(20,7 bar)
Hydraulic Pump Flow Test
With engine at FULL throttle, boom retracted, use the joystick to fully lower the
boom. Hold over relief. Check readings. If incorrect, adjust or replace cartridge.
Note: Perform this test with carriage removed.
With engine at FULL throttle, use the joystick to extend boom fully. Hold over
Port Relief relief. Check readings. If incorrect, adjust or replace cartridge.
CONSULT FACTORY
With engine at idle, load sense is 0 psi.
With engine at FULL throttle, use the joystick to fully retract the boom. Hold over
relief.
With engine at FULL throttle, turn the steering wheel all the way to one direction
and hold while checking pressure. If pressure is not correct, adjust or replace
the pressure relief valve cartridge.
With engine at idle, turn the park brake switch to disengaged position with
secondary function held over relief. Check pressure. This pressure is not
adjustable.
With engine at FULL throttle, move joystick to boom retract position. Hold joystick
over relief and check pressure. If pressure is not correct, adjust or replace the
cartridge in the secondary function manifold. If cartridge cannot be adjusted, consult
factory.
With engine OFF, depress and hold brake pedal. DO NOT overstroke the brake
pedal. Check both front and rear service brakes at the individual test nipples on
the brake valve. If pressure is incorrect, check for external leaks. If no leaks are
found, check accumulator pressure at test location 10.
With engine at idle, depress and hold brake pedal. DO NOT overstroke the
brake pedal. Check both front and rear service brakes at the individual test
nipples on the brake valve. Check pressure. If pressure is not correct, check
accumulator pressure at test location 10.
75-150 psi With the engine at idle, check the pressure on the stabilizer cylinder. If pressure
is not correct, adjust or replace the cartridge.
With engine at FULL throttle, turn the steering wheel all the way one direction,
and hold while checking pressure. This pressure is not adjustable.
At start up, the pressure should stop momentarily at 700 psi (48 bar), which is
the pre-charge pressure. The pressure should then continue to rise to 1950
±50 psi (134 ±3,4 bar) which is the accumulator charge pressure. Let the
system bleed down naturally with engine at idle (minimum of 2 minutes). The
accumulator charge pressure should recharge at 1050 ±50 psi (72 ±3,4 bar).
With engine at idle, check standby pressure. If pressure is not correct, adjust or
replace the differential pressure sense cartridge on the unloader valve.
Hydraulic System
Fittings
Unit equipped with fittings from factory.
Unit equipped with fittings from factory.
#4 O-Ring Boss Fitting with Diagnostic Nipple
Required for Stabilizer Cylinder
PRESSURE TEST PROCEDURES
9.11