Lull 944E-42 Service Manual - Manual (Page 377)

8.125 Model 644E-42/944E-42 Rev. 6/04
Hydraulic System
Not
OK
If there is no four-wheel or crab
steering, check the steer select valve.
Inspect/replace the steer select valve.
Not
OK
Not
OK
Front or rear wheels are not parallel
in front or four-wheel steering mode.
Perform indexing procedure on vehicle.
Check wheel alignment.
Not
OK
Check the steer select valve. Replace the steer select valve.
If OK
Refer to ZF Axle Repair Manual, Model
MS-T 3045, ZF part # 5871 550 002.
JLG part # 8990419
Not
OK
Check seals in steering cylinders.
If OK
Repair/replace steering cylinder(s).
If OK
NOTE:
When checking pressures
in circuits, refer to Section
8.7, “Hydraulic System
Testing,” for correct
pressure readings.
Not
OK
Repair/replace steering cylinder(s).
Check the power steering unit.
Replace power steering unit.
LSG &
P1
Pressure
OK
If So
If the steering is slow or difficult,
check the pressure at the “P1” port of
the accumulator charge/secondary
function valve by bottoming out the
steering and noting the relief
pressure.
Pump the brake pedal to start the
accumulator charge cycle and verify that
the pressure builds to high limit and
unloads pump.
Increase engine rpm to see if pressure
builds with higher rpm and steering
improves.
Not
OK
Check pressure at “P1” and “LSG” port
while bottoming out steering
If OK
If Not
Repair or replace pump.
Adjust/repair/replace pressure relief
valve in accumulator charge/secondary
function valve.
No High
Limit
No LSG
or P1
Pressure
Check the front and rear steering cylinders
for seal leaks. Shift to front only steer to
isolate front axle.
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