Leak
On the passenger side of the engine above the intake manifold there is a barrel shaped valve(HVAC related)that should have a grey line stubbed in to the front of it. It is not terribly uncommen for this to come off, def. check it first. Then start looking over the vaccum lines associated with the hub system would be next. Pretty basic, just look for a loose tube or one that may be damaged. Might even want to try a couple light thumps on the pump itself with a rubber mallet, just don't get carried away with your thumping. Pump should not run continuosly, should hear it run a little bit with the key on before starting. Hope this helps.