850 T-5R L5-2.3L Turbo VIN 58 B5234T5 (1995)
Vacuum Pump: Description and Operation
Vacuum pump and regulator
On a given signal from the control module, the vacuum pump and regulator control the negative pressure in the tube leading to the vacuum servo
which is attached to the throttle linkage.
When the vehicle speed decreases, the vacuum pump is started and this increases the negative pressure in the tube. lithe vehicle speed increases the
regulator lets more air in, so as to lessen the negative pressure. The vacuum pump is powered by an electric motor. It starts when the SET button is
pressed, causing the control module relay to cut in. This feeds current to the motor and connects it to ground. The motor drives the vacuum pump until
the vacuum servo has obtained enough vacuum to maintain the desired speed, as indicated by the speedometer through its input signal to the control
module. The control module then breaks the vacuum pump ground connection.
If increased throttle setting is required on a climb, the vacuum pump will start working again and increase the negative pressure until the set speed is
reached. Going downhill, the regulator vacuum valve opens and admits ambient air, thus reducing the negative pressure in the vacuum servo and the
throttle opening.