PS flow control value problems

[gsep]

I've got a 1987 Supra and have been having a bit of an issue on my hands. I had to replace my power steering pump to get my steering working well enough to pass inspection. So I replaced the pump. While bleeding it, the flow control valve, spring, control sprint seat and snap ring shot right out of the pump and onto the ground, and all of my fluid followed. I figured it was just a bad pump and picked up and installed another. This one seemed to be fine but, just a bit ago, the same thing happened (but not as bad. All of the above is still, technically, in the pump. The control spring seat is dislodged just enough for all my PS fluid to have shot out.). I'm not sure if the snap ring is still there. So either my car has another problem or I'm screwing up the installation. I think both times that the valve pushed it's way out I had the wheel turned to either one lock or the other. Any body have a clue as to what's going wrong?