Chrysler laser 1990 Technical Information Manual page 221

In
POWER STEERING - Oil Pump
OIL PUMP
The oil pump has a separate oil reservoir; it is a vane-type pump
that generates hydraulic pressure by the rotor, vanes and cam
reduce the power-assist effect during high-speed driving and
thereby improve steering stability) and a relief valve (in order to
maintain the hydraulic pressure and steering linkage rela-
t i o n s h i p ) .
NOTE
The relief valve is incorporated within the flow-control valve.
OPERATION OF THE OIL PUMP
The rotation of the rotor causes the ten vanes to move radially
by centrifugal force, and when there is rotation along the cam
curved surface of the circular cam ring, there is action in the
radial direction along the cam curved surface.
The fluid chamber is formed by the cam ring, rotor and vanes;
when the rotor rotates the inner surface of the cam ring
(circular), the fluid chamber pressure changes to negative
pressure, with the result that the fluid within the oil reservoir,
which is at atmospheric pressure, is drawn in (suction step),
after which the rotor rotates further, discharging the fluid
(discharge step).
The action of this pump is two intake strokes and two
discharge strokes for each vane during one rotation of the rotor.