Lull 944E-42, Service Manual

Page: 379 / 844

8.129 Model 644E-42/944E-42 Rev. 6/04
Hydraulic System
Not
OK
Check the flow at the end of the
circuit at the male coupler.
Repair/replace pump
NOTE:
When checking pressures in
circuits, refer to Section 8.7,
“Hydraulic System Testing,” for
correct pressure readings.
NOTE:
Before pressure checking
circuits, refer to Section 9.8.29,
“Dual Joystick - Auxiliary
Hydraulic Circuit &
Troubleshooting,” to ensure the
electrical circuits for the pilot
select valve are functioning
Not
OK
Check pilot pressure at “PPG” port
of accumulator charge/secondary
function valve.
Adjust/repair/replace
pressure reducing cartridge
on accumulator charge/
secondary function valve.
Not
OK
Check port relief at main control
valve
Replace the relief valve on
auxiliary hydraulic section of
main control valve.
There are no auxiliary hydraulic
functions.
Not
OK
Inspect pump. Refer to
Hydraulic Testing
pages 8.12 through 8.54.
Check the cycle times for boom
LIFT and boom EXTEND to
determine pump performance.
Pump flow directly controls these
cycle times. Refer to Section
2.5.6, “Hydraulic Cylinder
Performance Specifications,” for
correct cycle times.
Not
OK
Check the standby pump pressure
at implement pump pressure tap.
If OK
If OK
If OK
If OK
Replace unloader cartridge
on main control valve.
If OK
Not
OK
Adjust/replace main relief
cartridge on main control
valve.
If OK
Not
OK
Repair/replace front joystick.
Install pressure gauge in the pilot
supply line, between the rear
joystick and the extend/retract
section of main control valve.
Check pilot pressure. With the
joystick moved all the way to the
right, the pressure should be
444 ±22 psi (30,6 ±1,5 bar).
Check the main relief pump
pressure at implement pump
pressure tap. Refer to Section 8.7,
“Hydraulic System Testing,” test
sequence 7.
Install pressure gauge in the pilot
supply line, between the front
joystick and the auxiliary hydraulic
section of main control valve.
Check pilot pressure. With the
button pressed and joystick moved
all the way to the left the pressure
should be 444 ±22 psi
(30,6 ±1,5 bar).
Before troubleshooting any
hydraulic circuit, ALWAYS
begin by checking the
following:
1. Hydraulic oil level in the
reservoir
2. All hoses, tubes, fittings
for leaks, kinks,
interference, etc.
3. Air in the lines