2005 Chevy express 3500. 6.0

[Brenda Williamson Dubois]

Van starts fine cold but when warm you let it set 15+ minutes it has to crank over alot to get it to start and after that you can shut it off and restart no problem. No issues in preformance driving it. already change injectors and fuel pump which has the fuel filter enclosed.

Changed the cam shaft sensor, still the same, cold starts easy, then Prolonged start. Could it be the crank shaft sensor? How can i test it ? I have to pull starter to get at it. Thank you