Chrysler 1997 Stratus Convertible RHD Service Manual page 923

JX
DESCRIPTION AND OPERATION (Continued)
• Power steering fluid reservoir filler cap/dipstick
assemblies.
Because of unique shaft bearings, flow control lev-
els or pump displacements, power steering pumps
may be used only on specific vehicle applications. Be
sure that all power steering pumps are only replaced
with a pump that is the correct replacement for that
specific application.
Hydraulic pressure is provided for operation of the
power steering gear by the belt driven power steering
pump. It is a constant displacement, vane type
pump. The power steering pump is connected to the
steering gear by a power steering fluid pressure hose,
return hose and the remote power steering fluid res-
ervoir.
Rectangular pumping vanes in the shaft driven
rotor, move power steering fluid from the intake to
the cam ring pressure cavities of the power steering
pump. As the rotor begins to turn, centrifugal force
throws the vanes against the inside surface of the
cam ring to pickup residual oil. This oil is then forced
into the high pressure area. As more oil is picked up
by the vanes, the additional oil is forced into the cav-
ities of the thrust plate through two crossover holes
in the cam ring and pressure plate. The crossover
holes empty into the high pressure area between the
pressure plate and the housing end cover.
As the high pressure area is filled, oil flows under
the vanes in the rotor slots, forcing the vanes to fol-
low the inside surface of the cam ring. As the vanes
reach the restricted area of the cam ring, oil is forced
out from between the vanes. When excess oil flow is
generated during high-speed operation, a regulated
amount of oil returns to the pump intake side
through a flow control valve. The flow control valve
reduces the power required to drive the pump and
holds down temperature build-up.
When steering conditions exceed maximum pres-
sure requirements, such as when the wheels are
turned against the stops. The pressure built up in
the steering gear exerts pressure on the spring end of
the flow control valve. The high pressure lifts the
relief valve ball from its seat and allows oil to flow
through a trigger orifice located in the outlet fitting.
This reduces pressure on the spring end of the flow
control valve which then opens and allows the oil to
return to the intake side of the pump. This action
limits maximum pressure output of the pump to a
safe level.
Under normal power steering pump operating con-
ditions, pressure requirements of the pump are below
maximum, causing the pressure relief valve to
remain closed.
POWER STEERING FLUID PRESSURE SWITCH
On all vehicles, a power steering pressure switch
WIRING HARNESS CONNEC- POWER STEERING PRES- POWER STEERING GEAR SURE SWITCH TOR
(Fig. 2) is used to improve the vehicle's idle quality.
The pressure switch improves vehicle idle quality, by
maintaining required engine idle speed when neces-
sary, due to increased pressure in the power steering
system. This increased pressure will slow down the
power steering pump which will decrease engine idle
speed.
The pressure switch functions by signaling the
power train control module, that the power steering
system is putting additional load on the engine. This
type of condition exists when turning the front tires
of the vehicle when the vehicle is stationary and the
engine is at idle speed. When this condition is sensed
by the power train control module, through a signal
from the power steering pressure switch, engine idle
speed will be maintained. The maintained engine idle
speed compensates for the additional load, thus
maintaining the required engine idle speed and idle
quality.
The power steering pressure switch is mounted
directly to the power steering gear on vehicle's
requiring its use (Fig. 2).
Fig. 2 Power Steering Pressure Switch Location On
Steering Gear
DIAGNOSIS AND TESTING
POWER STEERING PUMP FLOW RATE AND
PRESSURE TEST
The following procedure is to be used to test the
operation of the power steering system on this vehi-
cle. This test will provide the flow rate of the power
steering pump along with the maximum relief pres-
sure. This test is to be performed any time a power
steering system problem is present to determine if
the power steering pump or power steering gear is
not functioning properly. The following pressure and
STEERING 19 - 9