LLY: Fuel bleeding problems

[Skyhigh4by]

Just got it back together after head gaskets. I had a thread on diesel place about it not cranking but got that solved (bad connection @ ECM) now it cranks over but I can't for the life of me get the fuel system bled out. When it was apart I dropped/cleaned the tank and blew out all the lines. It now has 10 gallons of fresh fuel in the tank.

Ive bled it many many many times and there is no more air coming out of the bleeder and the hand pump pressures up. Ive also confirmed that there is fuel getting as far as the cp3 but there is NOTHING on the other side of it. I pulled a couple injector return lines and while cranking get steady fuel coming out of the lines.

I pressure up the filter head and after cranking the primer pump is soft again. I can't see any leaks anywhere around the filter head.

Im sure I've done more to try to get fuel to the rails but my mind is a bit scattered from being so stumped. My theory is that fuel is getting to the CP3 and then being pushed from there down the return line and for some reason nothing is getting past the pump in to the rails.

Help please :dontknow:

 

[Skyhigh4by]

I'm showing 280ish psi rail pressure and no increase while cranking. I can get the primer pump hard but it goes soft after cranking. Took the line off the front of the driver side rail and there is no fuel present. Take return lines off at injectors and while cranking there is fuel coming out.

 

[Skyhigh4by]

Well I guess nobody has any ideas so I'll just keep talking to myself.

I removed the pressure and return lines from the cp3 and found that all the pressure created by the primer pump is just going down the return off the cp3 and nothing is going to the high pressure side. Is there a valve in the pump that could be stuck or something? All the fuel I get to the pump just ends up down the return and nothing is getting to the rails...

 

[gmduramax]

FPRV? How long did you try cranking for?

 

[Skyhigh4by]

I've been cranking for 3 days solid. There's no fuel in the rail and no air leaks between the tank and cp3. If I pinch off the return line from the cp3 and pump the primer hard it will stay that way for as long as I leave it. As soon as I take the clamp off the return the primer begins to loose pressure.

I've tried unplugging the fprv. I've also tapped on it thinking maybe it was stuck. It makes a very slight buzzing noise when key is on.

I have also tried forcing fuel back down the pressure outlet and return on the cp3 and they are both blocked off.

 

[Skyhigh4by]

Could the FPRV be stuck closed thus not letting the pump get any fuel? Is there any way to test it?

Ive been at this for 4 days now and not getting anywhere but closer to wearing out my starter and considering drowning it in ether until it either starts or blows up

 

[Skyhigh4by]

So just incase other ppl seem to have the same problem I solved it by taking the cp3 apart. I found the valves that let fuel in to the pistons were stuck with gummy old fuel. I removed and cleaned those and the cascade valve. Then I was able to bench test the pump with a hose out of a jerry can and spun it with a 1/2" drill to confirm that fuel was intact coming out of the pressure side. With the pump in the vice and the drill spinning at 500rpm fuel shot out of the pressure fitting about 15'.

Just for the ppl that might say thats dangerous because of the pressure ITS NOT. It would take ALOT of volume to compress enough to be even remotely dangerous out of an orifice that big.

Put it back together and it fired right up on second crank.