Correct. The pump won't prime with the ignition off.

 

Since "the center differential needs to become open to allow for the front set to turn at a different speed"...does that mean during a hard turn on dry pavement, the car is effectively just a front wheel drive car during the few seconds of the turn?

 

no, it is always 4x4.. even when the pump is broken.
what ACD does is just regulate slip between the axles.. in other words it is a hydraulically controlled limited slip

 

okay, got it, limits slip between front and rear axle just like an LSD limits slip between left and right tires on the same axle.

 

exactly