SUB-SECTION 4D
CONTROL VALVES
mended that the engine high speed and low idle speed be
and must correspond with the pressure listed on the pres-
checked and adjusted if necessary. A check of engine speed
sure decal.
should show a high speed of approximately 2750 RPM at
6. If the relief valve setting is incorrect, remove the acorn
no load and a low idle speed of approximately 600 RPM at
nut from the adjusting screw(see Figure 4D-13), loosen the
no load.
locknut and set the pressure by turning the adjusting screw
2. Operate the machine until the hydraulic oil temperature
in or out.
is a minimum of 70oF (21oC). Check the control valve
NOTE
spools to be sure they travel a full stroke in each direction.
Initially. back the adjusting screw out a few turns,
3. Shut down the engine and install an accurate 0 to 3000
allowing the valve poppet and seat to be flushed
psi (0 to 206.0 bars) pressure gauge in the gauge tee at the
thoroughly. Then turn the adjusting screw in to
base of the boom (see Figure 4D-14).
obtain the specified pressure setting.
NOTE
7. Repeat the above procedure for the relief valve in the
other valve section.
It may be helpful to swing the winch base downward
before installing the pressure gauge. This can be done
8. When the settings are correct, shut down the engine and
by supporting the winch and removing the upper
disconnect the test gauge. Clean and install the test tee cap.
Then swing the winch up and install the upper winch base
winch base bolts. Then allow the winch to swing
down and hang from the lower mounting bolts.
bolts.
TROUBLESHOOTING
Table 4D-7 lists the difficulties which may be experienced
with the valve and hydraulic system. It indicates the cause
and remedy for arch of the troubles listed. It should always
be remembered that pressure and delivery ore factors which
are usually dependent upon each other. Adequate pressure
gauge equipment and a thorough understanding of the
operation of the complete hydraulic system are essential to
diagnosing improper valve operation.
REMOVAL
Remove the valve assembly from the machine as follows:
1. Shut off the engine and tag the ignition switch in the
upper and carrier to warn against starting the engine until
the valve is reinstalled.
2. Clean the valve and fittings on it, with a suitable solvent.
Then wipe or blow away the solvent.
3. Disconnect the hydraulic lines at the valve and position
the lines to avoid interference as the valve is removed. Cap
the Iines and plug the valve port to prevent the entry of
Figure 4D-14. Gauge Ports
4. Disconnect the control Iinkage at the spools.
4. Start the engine and set the speed at approximately
5. Remove the bolts attaching the valve to the deck plate.
1480 RPM.
6. The valve can now be removed. Note the presence of
5. Operate the control valve, which controls the cylinder
any shims under one corner of the valve. The purpose of
with the test gauge installed in it, to retract the cylinder
such shims is explained at installation of the valve.
and hold the lever in the retract position briefly when the
cylinder reaches the end of its stroke. The relief valve will
OVERHAUL
by-pass, as indicated by a pressure drop, after reaching a
peak. The peak pressure represents the relief valve setting
GENERAL. All parts of the valve are serviceable, except
4D-19
