Vacuum leak? Marc has me confused now!

[mike100]

The secondary vacuum pump runs to first charge the mini reservoir which you hear with ign on. This is just a reserve to prevent a delayed response of the secondary diaphragms.

The vacuum pump will also turn on when you step on it and open the throttle blades enough for the manifold vacuum to drop or whenever the ecm sees appropriate engine load and minimum rpm etc to open secondary ports. The vacuum pump runs at about 13" of vacuum as long as it needs to sustain the secondary high power mode. Once you back off of it, the manifold vacuum rises anyways. The pump turns off once the mini reservoir is again 'charged'.

I observed this when I hooked up a vacuum gauge to my secondary diagnostic map sensor and watched it as I drove around.