06 Power steering issues

[LaserMan]

My 2006 V8 61K miles Explorer just started having problems with the power steering. When not moving (parked) the steering has 'power' for just a fraction of the steering wheel motion then seems to quit completely. No squealing, no belt slip, belt in good condition, fluid is clean and properly filled. Problem just started.
Pump? Ram? Other??

 

[waskly]

when you give it gas or raise the rpm does it get assist back if so you need a pump, if not you need a rack.