Hydraulic System 257
In a hot shift system, the pump is declutched when the PTO is disengaged. In that configuration,
there is no coil on the dump valve. The dump valve will regulate the hydraulic flow to 45 GPM. The
pump (PTO) switch found on the in-cab control panel controls the clutch engagement.
Single Vane Pump
EXPERT™ vehicles with no automated loading arm are equipped with a single vane pump (see Figure
5-1). This pump is usually front-mounted and is activated by an electric solenoid valve. The electrical
signal that activates the solenoid is sent by the pump switch on the control panel.
Figure 5-1
Single vane pump
The single vane pump powers all body functions (tailgate, body hoist, and packer) through the
directional control valve (see Directional Control Valve on page 258). It is capable of delivering a flow
of 20 gallons per minute (gpm) at 700 RPM. A dump valve located on the chassis (see Figure 5-2)
limits the flow to the valve to 45 GPM. All excess flow is sent back to the hydraulic tank. When the
pump is turned off, the oil returns to the hydraulic tank.
Figure 5-2
Chassis-mounted dump valve