Lull 944E-42 Service Manual - Manual (Page 263)

8.11 Model 644E-42/944E-42 Rev. 6/04
Hydraulic System
8.6.1 Pressure Checks and Adjustments
When diagnosing trouble in the hydraulic system, use the
hydraulic testing information in Section 8.7, “Hydraulic
System Testing.”
In general, follow the steps below whenever conducting
pressure checks and performing adjustments:
1. Park the vehicle on a firm, level surface. Engage the
park brake, place the travel select lever in the [N]
NEUTRAL DETENT position, level the boom and
turn the engine OFF.
2. Remove the access plate from the cab floor to gain
access to the diagnostic test fittings.
3. Pressure diagnostic fittings are conveniently located
under the cab floor and are for each hydraulic circuit
being tested. A decal (3) showing each diagnostic
fitting location and function being tested is located
on the underside of the access plate (4). Install a
pressure gauge capable of measuring at least 10%
more pressure than that which the circuit being
checked operates under.
4. Start the engine. Operate vehicle functions several
times to allow hydraulic oil to reach operating
temperature. The hydraulic oil temperature should
be between 100-120° F (38-49° C). If a temperature
gauge or thermometer is unavailable, the hydraulic
oil reservoir should be warm to the touch.
5. Refer to Section 8.7, “Hydraulic System Testing,” for
testing procedures.
6. Fully depress the accelerator pedal as required.
Place and hold the appropriate joystick in the
position needed to operate the particular vehicle
function being checked. Continue holding the
joystick in position until pressure readings are taken.
7. Check the pressure gauge reading. It should read as
specified in the Pressure Readings column of the
charts found in Section 8.7, “Hydraulic System
Testing.” If the reading is not as specified, turn the
engine OFF and check other components in the
system. Verify that all related hydraulic components
and electrical switches, sensors, solenoids, etc. are
operating correctly.
8. As a last resort, adjust the appropriate relief valve, if
applicable. Turning the adjustment screw clockwise
will increase the pressure; turning the screw
counterclockwise will decrease the pressure.
9. Start the engine and check the pressure again. Turn
the engine OFF, then disconnect or remove the
pressure gauge from the vehicle.
10. Reinstall the protective caps onto the diagnostic test
nipples.
11. Reinstall the access plate to the cab floor. Secure in
place with the capscrews. Torque the capscrews to
18 lb-ft (25 Nm).
4110392
1
6 5
4
3 2
Location Function Tested
1 Main Valve Pressure
2 Pilot Pressure
3 Park Brake
4 Pump #1
5 Accumulator Pressure
6 Load Sense (Steering)
7 Load Sense (Implement)
7
3
4
MU3920
WARNING:
Avoid prolonged engine
operation in closed areas with inadequate
ventilation. Failure to properly ventilate exhaust
fumes can result in death or serious injury.
WARNING:
Avoid prolonged engine
operation in closed areas with inadequate
ventilation. Failure to properly ventilate exhaust
fumes can result in death or serious injury.