2004 6.0 crank no start
 

I have 2004 6.0 stock no mods cranks and tries to fire first couple cranks then will just crank FICM voltage was very low changed the FICM I have 1300 psi oil pressure. I have fuel up at the secondary filter on top of the engine . I am at a loss. I use it as a truck not a grocery getter I pull trailers all the time. the starter acts likeit wants to kick out on it like I am losing voltage I made sure that I was not losing voltage still seems to want to kick out brand new starter just replaced flywheel any suggestions ??????????

CAM Sensor got me the first time, and the second it was a wiring harness.