How your log splitter operates, The pump, The directional valve and cylinder – MTD 243-638-000 User Manual
Page 15: Dperational problems
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HOW YOUR LOG SPLITTER OPERATES
Cylinder
□
^ Cylinder
Directional
Valve
Relief Valve
Breather
Cap Unloading
Valve '
Pilot
Pressure
Line
Pump
Reservoir
THE PUMP
A two-stage log splitter pump has one large and one
small gear section, using common inlet and outlet
ports. Below a preset pressure (called unloading pres
sure) a check valve between the two gear sections
allows both flows to combine. Together, the two gear
sections create a large volume flow which produces
rapid cylinder movement under low load conditions.
Above unloading pressure, a pilot pressure line
(which simulates actual pressure at the cylinder) acti
vates the unloading valve, which causes the flow to
bypass the large gear section and return to the pump
inlet area. The small gear section is now operating
alone, and will generate the higher pressure neces
sary for the actual log splitting operation.
The original factory setting for the unloading valve is
designed to provide maximum flow while remaining
below engine stalling load. Note: Splitting capabiiity
is not affected by the setting of the unloading
vaive. Do not attempt to adjust or reset it without
a pressure gauge (shouid be performed by an
authorized service deaier oniy).
THE DIRECTIONAL VALVE AND CYLINDER
From the pump, oil flows to a four way, three position
directional valve. At the neutral position this valve
directs the flow back to the oil reservoir, bypassing
the cylinder. When the directional valve is directing
the flow to the back of the cylinder, the cylinder rod
extends quickly until it meets significant resistance.
Upon reaching unloading pressure, movement of the
Low Volume
High Volume
High Pressure
Low Pressure
Gear Section
Gear Section
shaft will slow but will continue forward. If the pres
sure reaches a preset maximum (called relief valve
pressure) the relief valve, located within the direction
al valve, will allow the flow to bypass the cylinder and
return to the reservoir. This can happen when the
cylinder rod meets excessive resistance, or when it
reaches the end of its stroke and can move no farther.
NOTE: Never operate at relief valve pressure for
more than a few seconds.
When the directional valve is directing the flow to the
front of the cylinder, the rod will retract quickly since it
is encountering no resistance. The relief valve will
momentarily bypass the flow at the end of the return
stroke but the directional valve should then automati
cally return to the neutral position, directing the flow
directly into the reservoir. This serves to protect the
pump from possible damage due to prolonged opera
tion at relief valve pressure.
Because of the potential for system damage, the relief
valve is carefully and precisely preset by the manu
facturer.
NOTE: The user should not attempt to adjust or
change the setting of the relief valve.
DPERATIONAL PROBLEMS
If you have trouble with your log splitter, please refer
to the Hydraulic Trouble Shooting Guide.
NOTE: Readjustment of valves or disassembly of
pump should be performed by an authorized ser
vice dealer only.
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