CP3 issues

[junkyarddog]

This is going to drive me crazy, please help! I just did a long block swap on a 2005 cummins 5.9 common rail. The truck drove to my house knocking, I installed the new motor and it would not fire up. It runs off of ether but dies as soon as you stop feeding it. There is plenty of fuel to cp3 but it does not build pressure from the output side to the pressure rail witch i capped off for pressure testing. I installed another used cp3, and had the same problem. So I ended up getting a new one. The new cp3 only builds about 130 psi. not even close to the desired 4000 psi it should have at idle? I would rule it out to be a problem with the ecm, however, I am reading accurate data from the ecm on my scanner, I re-checked all my grounds, made sure there is plenty of fuel to the pc3 and cranked the engine with the cap off to make sure the pump isnt spinning on me. I have exhausted all my ideas and i can not come up with anything... somebody smarter then me please help me out

 

[cerberusiam]

Unplug the FCA and see if it will build pressure. How much pressure is at the CP-3 inlet? Plenty fuel may not be enough fuel to build adequate pressure without adequate flow.

 

[Bob4x4]

Suspect an injector/install concern first

 

[sag2]

You can do a cranking fuel return test. You have to crank it in 20 second intervals allowing the starter to cool in between. Also if you completely block off the air intake at the air horn it will not have any compression and will spin over faster doing the return test. My guess is also connector tubes or improper injector install.