Hello my 93 5.0 engine runs great 99% of the time but usually on a weekend where I haven't ran it at all on a Saturday I'll come out on a Sunday and it'll crank over and crank over and crank over and won't start if I pump the crap out of it and I mean a lot it'll try and try and then eventually start but not always. Then it'll just sit for another day or two and I'll try it again and will fire right up and run great no problems of any kind. Any help or suggestions would be greatly appreciated. Thank you.

 

Do a fuel pressure test when it cranks and won't start. Sounds like it might be a fuel problem.