LLY fuel pressure issue

[ikeG]

I am scratching my head over a LLY truck here. Came in with low rail pressure and extended crank symptoms. Truck would make max of 12k rail. Fixed his leaking filter head but still have both issues. Bottle tests indicated CP3 was the worse offender, both it and the injectors return a bit. Put a Bosch reman cp3, it fires up 2nd try. Idled at desired rail for a minute. But after shutting it off, it has yet to restart. Will make a max of 1300 psi, but takes 6-7 seconds to get there. Clear line between the filter and ficm has no air bubbles. Whats weird is the pressure from pumping the primer bulb will bleed off out the cp3 return line. It also makes anywhere from 60 to 80 ml of fuel doing the bottle test. Injectors(all 8 combined) make 30-40 ml. FPRV is not leaking.

I had the fuel injection shop drop off another pump, but im hesitant to install it for fear of paying for 2 if they are not bad. Sure sounds like a bad pump tho

 

[2004LB7]

could it just be a bad return valve on the CP3 or some debris holding it open? you might be able to get to it without having to pull the cp3

 

[ikeG]

So 3 different cp3s in it now. His original, a new reman bosch, and a known good OE lly. All with the same extended crank-to-start, 12-13k max rail psi. Each pump fails the return rate test. Cranking for 15 sec, ficm unplugged, cp3 returns 60-80 ml. I've replaced the entire feed line, switched another filter head, new fuel filter etc. Tested the PRV at least 3 times now. He brought it here after installing a new sending unit, i havent verified its condition....

What am i missing here?

 

[gmduramax]

Isn’t 30-40ml for the injectors right at the limit or past?

 

[ikeG]

Yes that is at limit. But the cp3 is the worse offender based on our tests.