a friend of mine has a 2001 Savana 5.7 ls1 . When it sits after driving, it ill not start. It turns over like it is out of gas. give it a shot of carb cleaner and it starts right up and runs fine.
Any ideas as to why?

 

If it still has the old 5.7, it probably has the old spider style poppet injectors. Which are very sensitive to fuel pressure. When the fuel pump starts thinking of going bad, they refuse to start, but will run just fine once started.

Check fuel pressure on starting. Even being at the bottom end of spec can cause it not to start sometimes.