2000 Hyundai Elantra Won't start on first crank

Hi Joe,
I hooked up a fuel pressure gage and with the engine running it is 36 psi and when I disconnect the regulator vacume line it goes to 44 psi which is spec. However, when I shut the engine off, it goes to 0 in about 3 seconds. The Haynes manual I have said that this condition is a defective check valve in the fuel pump and to replace the pump. In that this was the reason I replaced the pump in the first place and when I did replace it, it made no difference; I am hard pressed to believe that replacing it again will fix it this time and I would rather not spend another $140 unless I can know for certain it will fix it. I checked all the lines and did not find any kind of a fuel leak all the way back to the gas tank. Any suggestions on what to test would be appreciated.
Thanks

Hello, I did the line pinch test and the pressure held for 10 minutes before I released it so the problem appears to be a fuel injector or the regulator. Is there a way to test the regulator to see if it is the problem before I have to oull the injectors? Thanks for your help.

The problem is fixed so I thought I would add this to this chain. When I blocked the fuel return line and cranked the engine, it started to drop pressuer when I first turned it off but then it held it at 30psi and continued to hold it at 30psi until I bled off the pressure after 10 minutes. This told me that the fuel injectors were not leaking or else it would have bled off immediatly so the problem appears to be the fuel pressure reulator leaking fuel back to the tank on engine shutoff. I ordered the part, but before I could get it installed, the engine now starts right up like it is supposed to and I have not had any more problems with it. If it gets worse, I will replace the regulator but for now if it ain't broke, I ain't fixxing it. Thanks for pointing me in the right direction. This is an awesome website!