Use a screw driver and set adjusting screw as follows:
a.
Run the pump at low operating speed (approximately 1/4 of full engine rpm) but fast
enough so that the pump is developing the required pressure.
b.
Operate the control valve at its extreme position long enough to get a pressure
reading on the gauge.
c. Turn the adjusting screw clockwise to increase pressure or counterclockwise to
decrease pressure until desired setting is obtained.
d. Hold the adjusting screw, tighten jam nut and install and tighten acorn nut.
e. Retest to check pressure setting.
NOTE: Results of the above settings will indicate a relatively constant relief valve
setting across full engine rpm.
RELIEF VALVE REPAIR RECOMMENDATIONS
The cartridge type service port reliefs used in the swing valve are of the pilot poppet type
with external adjustment. Any malfunctioning is usually the result of foreign matter lodging
between the piston, relief valve poppet, and check valve.
To perform service, clean the surrounding area and remove the complete relief valve
cartridge. Examine the seat in the main valve housing for grooves or ridges. If damaged,
either replace the valve or have it re-machined.
The design of the pilot poppet and its seat provides positive seating and very seldom
requires any maintenance. The pilot section can be removed from the cartridge housing
without disturbing the setting.
With it will come the check valve poppet and other internal parts. These are easily
disassembled and should be examined for foreign matter. All seats and seating surfaces
should be free of nicks, scratches, or grooves. Examine “O” rings and back-up washers for
any damage. If any parts are found to be faulty, replace the relief cartridge. All moving parts
should slide freely, with only seal friction being present. After inspecting and cleaning,
immerse all parts in hydraulic oil and reassemble. If pressure setting was not disturbed, unit
can be tested for proper functioning under normal working conditions. If operating
difficulties indicate that the pilot poppet is still leaking or sticking, replace the relief.
OUTRIGGER RELIEF
Use the 4000 psi test gauge and check as follows:
1. Attach the gauge at the quick disconnect on the diverter valve (B), located on the L.H.
side of the front outrigger box.
2. Start engine and run at full throttle.
3. Set the outrigger extend/retract switch to the retract position and read the gauge. The
relief is located above the outrigger diverter valve. Adjust to proper setting as listed in
chart below:
T300-1_T500-1_T780
Service / Parts
482 P/N 12261-683
REVISED: January 2015
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