Vacuum timing system

Claim 1

A vacuum operated timing system for use with an electrical accessory circuit of an internal combustion engine having a variable vacuum source, said system including: an electrical switch connected in said accessory circuit; vacuum motor means connected to said switch rendering said switch closed below a first selected level of subatmospheric depression in said motor means; a flow restrictor communicating with said vacuum motor means; wherein the improvement comprises a vacuum regulator communicable with ambient atmosphere, with said variable vacuum source and with said vacuum motor means, said regulator including means limiting evacuation of said motor means to a second selected level of subatmospheric depression lower than said first selected level of depression while said engine is operative regardless of variation in the level of said vacuum source, said vacuum regulator further including means arranged for permitting air bleeding of said vacuum motor means through said flow restrictor when said engine is rendered inoperative; whereby said switch is retained in closed condition for a selected time interval after said engine is rendered inoperative.