Lull 944E-42 Service Manual - Manual (Page 148)

Hydraulic System
8-32 944E-42
8.7.13 Accumulator Charge/Secondary
Function Valve
Hydraulic oil from the front pump flows into the
accumulator charge/secondary function valve and then is
directed to the power steering unit, the two accumulators
which direct pressure to the service brakes. Oil also flows
from the accumulator charge/secondary function valve to
the main control valve, the park brakes in the front axle
and also provides pilot pressure to the joysticks.
The accumulator charge/secondary function valve is a
machined block with ports for various valves, cartridges
and other fittings. The accumulator charge/secondary
function valve (1) is located on the valve plate which is
located under the cab floor.
a. Accumulator Charge/Secondary Function Valve
Replacement
1. Park the machine on a firm, level surface, level the
machine, fully retract the boom, raise the boom, place
the transmission control lever in (N) NEUTRAL,
engage the park brake and shut the engine OFF.
2. Place a Do Not Operate Tag on both the ignition key
switch and the steering wheel, stating that the
machine should not be operated.
3. Open the engine cover. Allow the system fluids to
cool.
4. With the engine OFF, relieve the hydraulic pressure
from the accumulators. Apply the service brake
pedal and then release. Do this several times until all
hydraulic pressure has been relieved from the
accumulators.
5. Properly disconnect the batteries
6. Remove the access plate from the floor of the cab.
7. Label, disconnect and cap the hydraulic hoses and
the electrical plugs connected to the accumulator
charge/secondary function valve.
8. Swing the valve plate down. See Section 4.7.1,
“Valve Plate Removal,” for removal procedure.
9. Remove the accumulator charge/secondary function
valve from the valve plate.
10. Wipe up any hydraulic fluid spillage in, on, near and
around the machine, work area and tools.
b. Accumulator Charge/Secondary Function Valve
Disassembly, Cleaning, Inspection and
Assembly
1. Secure the accumulator charge/secondary function
valve assembly in a suitable bench vise if possible.
2. Tag and remove all hydraulic fittings, test ports,
cartridges, switches and compensator, noting there
location and orientation.
3. Clean all components with a suitable cleaner before
inspection.
4. Inspect internal passageways of the accumulator
charge/secondary function valve for wear, damage,
etc. If inner surfaces of the valve DO NOT display an
ultra-smooth, polished finish, or components are
damaged in any way, replace the valve or
appropriate part. Often, dirty hydraulic fluid causes
failure of internal seals and damage to the polished
surfaces within the accumulator charge/secondary
function valve.
Note: ALWAYS replace seals, o-rings, gaskets, etc.,
with new parts to help ensure proper sealing and
operation. Lubricate seals and o-rings with clean
hydraulic oil.
5. Secure the accumulator charge/secondary function
valve assembly in a suitable bench vise if possible.
Note: Refer to the Parts Manual for the correct seal fits.
MU5952
B
A
1