XJ-S V12-5.3L (1982)
Vacuum Switch: Description and Operation
The contacts of this switch are operated by a spring loaded diaphragm in a chamber. This senses inlet manifold vacuum such that, when the depression
falls below a certain value e.g. when the engine is operating at low speed, with part throttle near full load condition, then the contacts close. The closing
contacts causes the fuel system to go "open loop" and simultaneously introduce a fuel enrichment of 12%.
