1998 Isuzu Amigo fuel line

I replaced the fuel pressure regulator and it still has a problem starting. I have to turn the key over awhile before it catches. Like fuel isn't getting all the way up. When I drive there are no problems. After driving awhile it will start right up, but if it sits up awhile it takes time to start. What needs to be done? Do I need to pressure up the fuel line where the F. P. R. Sits in? Or is there something else I should do to resolve this problem? My # is 832 893 1246 if you would like to call.