Hydraulic system – Lull 944E-42 Service Manual User Manual
Page 393
8.141
Model 644E-42/944E-42
Rev. 6/04
Hydraulic System
Not
OK
Check the flow at the end of the circuit
at the female 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,
Troubleshooting,” to ensure the
electrical circuits for the pilot
select valve are functioning
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
Check the standby pump pressure at
implement pump pressure tap.
If OK
If OK
Replace unloader cartridge
on main control valve.
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
Inspect pump. Refer to
Hydraulic Testing
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.
If OK
If OK
If OK
Not
OK
Adjust/replace main relief
cartridge on main control
valve.
If OK
Not
OK
Repair/replace joystick.
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 joystick &
pilot select valve and pilot select valve
&auxiliary hydraulic section of main
control valve. Check pilot pressure.
With the button pressed and joystick
moved all the way to the right 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