lbz to a lly engine swap -- no start condition

[jbrett]

I have a 2006 C4500 had a running lbz in it with a hole in the piston. pulled it and put a lly in and all my lbz components on it accept the injectors. It is throwing the P0087 code for low fuel rail pressure can give it a shot of starting fluid and it fires but will not fire on its own I am pulling my hair out at this point can anyone give me some insight on this

 

[TheBac]

Did you cut the tooth from the reluctor wheel?

LLY vs LBZ Reluctor Wheel.

Somebody called and asked about this: 3 holes on LLY, 4 holes on LBZ. 57 teeth LLY, 58 teeth LBZ. Same apparent "timing" based on TDC indicator and timing holes. Both based on a 60 tooth wheel, with 3 or 2 teeth removed.

www.duramaxdiesels.com

 

[jbrett]

I changed the reluctor ring and gear that problem went away and the low fuel rail pressure started never threw the P0087 before i changed the relutor ring. what i don't understand everything ive read has said it only takes 2500psi to fire and im getting between 6,000 and 8,500 on the scanner. but as soon as i crank it over i loose prime

 

[2004LB7]

Check your fuel return at the CP3, injectors, and pressure relief

And I don't think you're getting 6000-8500 psi before cranking. Usually the most is a few hundred. Then it goes up as you crank. If it doesn't go up, you either have an air leak or restriction on the supply to the CP3, excessive fuel return or a bad CP3.

 

[jbrett]

I have checked all of that and i know the cp3 isnt bad it was in the truck on the lbz 3 days prior running with excessive blowby. And yes when watching the computer when cranking it starts at about 144 psi then builds up to approx 8500 thenstarts dropping back down.

 

[Zalathar]

Double-check the fuel rail pressure sensor, CP3 pump, and fuel lines for leaks or restrictions.

 

[Bdsankey]

Did you use your LBZ CP3 pump? What reading are you getting for rail pressure while cranking? Do you have any high pressure leaks? Any suction side leaks or collapsing lines?