ok I hope I am getting close to getting this thing fixed.
but the problem I have now is that when i first turn the key on the pressure jumps up to neer 50 but soon as the pump shuts off it drops rapidly and will only come back up if i crank the motor over.

What could cause the pressure to drop like that?

I had no problems with the pressure befor but had a bad injector so I took it all apart and replaced the injector put it all back together and now it just cranksand dose not start.

The pressure is under control of the pressure regulator, and is supposed to drop about 10 PSI after the engine starts. However; it is supposed to hold at the lower pressure once the engine is turned off. There could be a bad check valve in the fuel pump, a bad pressure regulator, a leaky injector, or a plain old fuel leak.