46 to atmosphere chamber space 42 is communicated via a nipple 54 to intake manifold vacuum chamber space 42 is totally enclosed except for the communication that is provided via nipple 54 whereby the sole means of fluid ingress to and egress from chamber space 42 is via the nipple a helical coil spring 56 acts between an internal wall portion of body 12 and diaphragm 36 to resiliently bias the latter in a direction away from valve seat 38 the central region of diaphragm 36 contains within chamber space 34 a valve element 58 that is adapted for coaction with seat 38 a central region of diaphragm 44 contains a stem 60 that projects with chamber space 42 toward and for coaction with the central region of diaphragm 36 the area of diaphragm 44 is made slightly larger than that of diaphragm 36 when the engine is not operating solenoid coil 30 is not energized and thus the flow path through cps valve 10 is closed by virtue of valve element 22 seating on seat 20 concurrently the three chamber spaces 34 42 and 46 are at atmospheric pressure for this condition spring 56 forces diaphragm 36 against the tip of stem 60 and both diaphragms downwardly to where diaphragm 44 bottoms out on the inside of closure 48 when the engine is operating manifold vacuum is delivered to both chamber spaces 34 and 42 the atmospheric pressure in chamber space 46 will therefore urge both diaphragms upwardly increasingly compressing spring 56 in the process stem 60 maintains a spacing distance between central regions of the two diaphragms the extent to which the diaphragms are displaced is a function of the intensity of manifold vacuum.