need help please

[bigrigdieselguy]

As the user name implies i work on semi's the smallest motor i touch is a 12.7 but i recently took on a project for a friend and his little 5.9 common rail is kickin my butt the truck turns over fine but will not start at all ive checked pressure from lift pump and its a steady 7.5 my scan tool showed the cp3 was only putting out 19 and spiked to 50 while cranking so i repaced it big mistake seeing as i got no results pressures are same as before ive since then capped off one injector at a time to see it was a leaky nozzle or cross tube with no luck in find the problem the truck has no mods is a 2005 2500 and it just broke 200,000 miles

 

[TFucili]

Hopefully one of the resident techs chimes in for you. Just a WAG, but what about the rail relief valve?

 

[Hoefler]

Have you check the fuel regulator??

 

[sag2]

Did the problem start as a progressively harder to start engine, or did it run fine one day and quit the next? Most likely you have a big leak on the high pressure side. First check the pressure relief valve. When cranking you should not have fuel coming out of it at the rail. Then the next most common problem is leaking connector tubes. Tighten each one to 37 foot lbs. I have several cap off tools, just in case more than one tube or injector is bad.
Also you might attempt to start it with starting fluid (being very careful to use very little). If it lights off and builds rail pressure normally you have a leaking tube or injector.