Fuel regulator/fuel pump

I own a 92' astro van 4.3L with 132000 miles, the 8th letter is a W. I started having problems with the start, have to wait a few seconds with the swith open and then started, but the car emited a lot of dark exhaust gases, so I took it to a friend and he noticed that the fuel pump and the regulator were in bad conditions so I changed them, also with the injector vortec. After that the car started good, and run smooth and fast, but the light engine repair soon lighted up, the next day the car did not start so I towed it to a dealer. They say that the fuel pump is only pumping 10 psi, so they changed it, and when I saw the pressure with the test gage was 45 psi, also they say that the fuel regulator is bad. Please, would you tell me what happened? Why the fuel pump and fuel regulator within 1 day just died? What is the cause that these elements just spoiled?
I appreciate your expertise and your answer
thank you
Xavier