Cp3 questions

[02greysixer]

So while my truck was down I figured I'd send my injector pump to get checked out. Sent it to a diesel shop my machine shop recommended and the place just called me. I know nothing about these pumps so I want yalls opinions too. He said that when he put it on his machine it wasn't making near the pressure it should (forgot to ask what psi it did make) be so he disassembled it. He found one of the pistons in the pump was seized, another was sticking, and only one was working properly. Is this something that happens to these? It doesn't surprise me there's something up with the pump because the truck always acted like it wasnt getting all the fuel it wanted. It threw a low rail pressure code one time right after I changed the fuel filter the day before the injectors went out.


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[McRat]

If only one piston was working, you'd end up with about 170rwhp, down from 250rwhp stock. It would be very noticeable.

How did I get this number? When you max out the CP3, you get about 500rwhp worth of fuel.

Even one piston should make full pressure, 23k. It's not a progressive pump, it's 3 single stage pistons.

What is odd, is that normally these are replace items, not rebuild items. It's a precision honed hardened steel bore and piston.

 

[02greysixer]

Thanks! That sounds about right, the truck was pretty much a turd. I thought that was just how the zf6 trucks were until they had some good tuning. Boy was I wrong. The guy said it was fixable but I'm going to just tell him to order me a new one and be done with it.


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[Colt]

23k psi will make you happy. New one must be about same money as rebuilder down there. Check your rail pressure after you change it consider lift pump to help CP3 with fuel supply. Even a Raptor will help your press. Airdog sells them.

 

[02greysixer]

Well the guy actually said it was a remanned one he'd sell me and I think he said $500, don't remember for sure. Hes supposed to call me back tomorrow. I was busy and couldn't talk much when he called today. But yeah I installed a lift pump when I did the injectors. Its the Air Dog with the pump, water separator, and filter all in one. Off road diesel is what killed this one


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[SmokeShow]

New lbz pump from GM is like 650-700 iirc.

 

[02greysixer]

Yeah I asked my dealer for the hell of it last week when I was there. They said for my truck it was $700ish. Don't remember the exact number


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[McRat]

I'd get a new LBZ item. IIRC, I pay about $600 for OEM.

The regulator is 90 deg different from the LB7, but with some minor work, it can fit, or you can just reuse your LB7 regulator and save the LBZ piece.

The LBZ part is improved and about 10% more fuel.

I'd be leary of a reman piece. There isn't a lot parts that can be reworked, so you will probably get a worn pump with the busted parts swapped out.

 

[02greysixer]

I didn't realize it was possible to use the lbz pump with my engine. It'll hook right up (minus the regulator issue) and the computer will be happy?? I don't have access to efi to customize anything


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[SmokeShow]

yep, just put your old (or a new) LB7 reg in place of the LBZ reg. and it'll be good to go, no tuning neccesary. IDK if you'd still see the 10% better flow out of it that way though? I kinda thought the better flow in the stock pumps was due to the regulators? Maybe I'm off base there though?

 

[Operator1]

You will need efi if you use the lbz regulator. I put an lbz pump on mine, and the regulator didn't work, so I put the guts of the lbz reg in my old one. Once I got the tuning right, it does pretty well.

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