Merkur Xr4ti L4-140 2.3L SOHC Turbo (1985)
Barometric Pressure Switch: Description and Operation
Fig. 15 Ignition barometric pressure switch
XR4TI
The ignition barometric pressure switch, Fig. 6, is used to control spark timing and/or other electrical devices in response to changes in barometric
pressure (altitude). When controlling spark timing, the ignition module is made to vary the spark timing by an amount determined by calibration resistors
in the switch assembly. In normal operation, spark timing is increased for engine operation above the pre-determined switching point (increasing
altitude) and retarded for engine operation below the pre-determined switch point (decreasing altitude).