lb7 shut off and wont start back up...PLZ HELP!!!

[boostedmax]

im working on a 04 lb7 truck....driving it down the road one day and it shut off and wont start back up...early that morning itwas idling odd and i thought it was just cuz it was cold out cuz it is tuned and has a cam and 75% over injectors.
history on what i have done.....
3 days before it shut off the injectors were replace
i have swapped ficm and ecm and cp3 pump and still wont run. These parts all came off a running truck. it will start on ether then die.
has a new fuel filter also and a ppe pump on frame rail.
its getting fuel to filter fine.
I scanned it with a tech 2 and the rail psi is 170-250 and desired is 6900....

If someone could give me some hints on what to try next im open to do whatever....(even burn it down haha)

Also i wonder about the crank sensor if it has something to do with it but the tech 2 said it was reading correctly

 

[DirtyMaxx03]

well if it starts on ether and dies, its not getting fuel. your rail pressure is obviously the issue. Unplug the regulator from the cp3 and log rail pressure. did you use a different FPR when you switched cp3's or the same one? it could also be a faulty rail pressure sensor???

 

[BM4LIFE]

^^Agree def not getting fuel. have you tried to have someone pump the primer ball while cranking. a known issue for these trucks is a cracked filter housing allowing air into the system. also check the o ring on the filter. not trying to down play the situation but i like to try the small things first

 

[LReiff]

You have a tech2 and the only engine data you give us is a low rp reading?
What codes are in the ecm?
What voltage is being commanded to the fca?
What voltage is coming back from the rp sensor?
How much fuel pressure is the lift pump making?
Have you checked injector return rate with a clear hose into a container?
Have you checked relief valve return rate?
You replaced the injectors with what? New? Reman? Whose remans?
Is there fuel in the motor oil?