I have a 96 GMC that when it is cold it will start right up but after you start it up the first time the next times you go to start it it just cranks over and over and takes a while to start but it does end up starting and I know the fuel pump is good and I have changed the fuel pump relay
I had a similar problem with my 1992 Buick Century (also made by GM). It started cold, but after warm-up and shut-off, I had problems re-starting it. It was a faulty fuel pressure regulator, located just before the fuel injectors. It was allowing too much pressure to be applied to the injectors. As a result, I was trying to restart a flooded engine.