starting help please

Hi....I have a 1995 yukon 5.7 tb....been having problems starting. Cold start requires 5-7 seconds of cranking. a warm start requires alot of cranking and sometimes it will not start at all. I've changed the fuel filter put in new plugs...no differance.I can hear the fuel pump run...after much cranking i can smell gas under the hood....so it seems the fuel pump is working....any help would be for a weekend mechanic would be great..

thanks in advance...kern

Had this issue with my 00 XL. Turned out to be the fuel pressure regulator.