I have never had one stop completely. Usually they are just noisy and the oil is all foamy when they have air in them, but they still work. Getting all the air out is a problem with Fords, and I believe the dealers had a vacuum device they fit over the reservoir to try to get it all out. But like I said, that's just to reduce the pump noise, otherwise they still work.

Take the line off the steering box and also the belt off the pump, and see if when you turn the pulley by hand, you get oil out of the pressure line.