I know it's a dumb question here. 2005 5.9. Have 5000psi rail pressure. Have rpm and cam and crank sensor both showing good. No start condition. Pulled line loose on top of relief valve. Just alittle fuel. I did pull mprop connector loose for high pressure. It'll sometimes start and run for about 7 sec then will not start at all. What am I over looking.

 

No codes.

 

Try unplugging FCA on cp3 pump, that is plug on the front of pump, try it.
Do you still have stock fuel pump ?
Take fuel line off going to cp3, put in bucket and turn key on, is
it pumping fuel. Do not loosen any fuel lines and try to start, they are high pressure.

 

check all grounds and battery connections. make sure they all clean, tight and not broken or cracked. look at the fan clutch wires too.