I have an '90 Ford F-150 where turning to the left is no problem. However, turning to the right is another story (like no power steering). I just installed a new power steering pump. Did not fix the problem. If I jack the front tires off the ground, it turns fine with the engine running and with the engine off I can manually move the wheels (turn). With engine running and one wheel on the ground it turns fine but with both wheels on the ground it is back to left OK and right bad. Your help is appreciated.
Slow450

 

Sounds like you need to replace the steering gearbox. If the ps pump was bad it would be hard to turn both directions not just one.

JR