LB7: 03 LB7 won't start after changing CP3 pump

[Meltd0wn]

I've been through a few threads about CP3 pumps, air leaks in the fuel system, and injector problems, but I have yet to see anything that can solve this one. I have an 03 LB7 with about 260,000 miles on it. I was getting the typical white smoke at idle problem so I installed all new injectors and high pressure fuel lines. The truck ran great, and I drove it for a month, but then I got the great idea to change the CP3 pump because of the mileage. Of course, now I can't get the truck started again. I changed the fuel filter housing, filter, and low pressure hoses. The truck still wouldn't start. I disconnected the return line at the quick disconnect, clamped clear tubing onto the return line and ran it into a container. I noticed that when pump up the system with the hand primer, it pumps up hard, but slowly loses pressure as the fuel trickles from the return line into the container. Is fuel supposed to come out of the return line just from the primer pump pressure? When I crank over the truck, no more bubbles come from the return line, so it's not sucking air anywhere. I loosened the high pressure fuel line nut on cylinder 7, cranked over the engine and fuel poured from the fitting, and also slowly from the return line. How do I know how much pressure is in the rail? I have no idea where to get a pressure gauge that can handle those high pressures. I rented a code reader, and the only code showing was P0700 (Tran Ctrl Sys Error). Anyway, the fuel system isn't sucking air, but I just can't get the truck to even sputter..any ideas?

Edit: I unplugged the jack from the FPR and that also did nothing. I'm beginning to wonder if the fuel pressure relief valve is stuck open.

 

[catman3126]

First how much fuel do you have coming out of te high pressure fitting on the pump when cranking? If none then pull the oil fill pipe and have someone crank it over and verify that the shaft is turning and that the gear is not slipping on the shaft. If it is turning and there's not fuel coming out of that fitting then something g is wrong with the pump you installed? Is there any chance that you mixed up the two rubber hoses for supplying fuel to the pump and the return hose? I doubt that but just a thought.

 

[Meltd0wn]

I loosened the high pressure fuel line nut on cylinder 7, cranked over the engine and fuel poured from the fitting. How can I find out how much pressure is in the rail?

 

[CHEZELTINE]

I used a snapon scanner to read rail pressure when my cp3 failed. I was told rail pressure has to be at least 2k before it will fire.

 

[CHEZELTINE]

If you did a sound job of replacing the cp3, its a good possibility you're relief valve is popped.

 

[Meltd0wn]

I'm pretty sure it's the relief. Probably the spring is broken. I'm tearing it back down far enough to take that valve out and check it. I also ordered a low pressure fuel line kit, so I'll start with those two things. Over on the diesel bombers site, there's a few pictures of a simple way of fixing the problem. The banjo bolt in front of the relief valve is tapped for a 1/2" plug. I thought it is was a pretty ingenious idea, so I'll try it before I put everything back together. Thanks for the tips. :thumb:

 

[Meltd0wn]

Okay I checked all of the hoses, routing, clamps,etc, and I plugged the end of the banjo bolt that the FPRV would dump into, and still no sweet diesel engine noise. I pulled the oil filler neck like catman3126 suggested, and as soon as the wife gets home, I'll have her crank the engine while I watch the end of the pump shaft. I'm still miffed as to why I get fuel down the return line when I pump the primer by hand. It pumps up hard but slowly leaks into the return line. The only place for it to do that is in the pump relief, or through the FPRV, which can't happen anymore. :dontknow:

Edit: I'll mark the shaft bolt and the gear to see if they move apart...don't need the wife for that!

 

[02greysixer]

You sure all the wiring is right? Both bulk connectors and ficm plugged in? Who's pump is it? Bosch reman? Used? Without a good scan tool capable of reading rail pressure and dtc's you're grasping at straws. But if the truck ran before, you have good fuel supply, everything is hooked up correctly and you didn't get a bunch of trash in the high pressure line to ruin injectors I'd be contacting whoever you got the pump from. Lb7 fprv pretty much never fail at or near stock max fuel rail pressure levels. Especially not at cranking/idle rail pressure.

 

[Meltd0wn]

Okay I marked the nut, gear and shaft with a sharpie, and took video. It's spinning without any slippage. I am just completely baffled now.

 

[Meltd0wn]

Yeah all the connectors are in place. It's a Bosch reman from Pensacola diesel. I called them and they said they don't do the rebuilds themselves. I'm meticulous about keeping fuel ports covered when I have things disassembled. You're right, though, I need to know what pressure the pump is putting out before I go any farther. I may just go get a 5K psi gauge from work and connect to the pump output to see what I get.

 

[Tothemax]

If you have every fuel line and electrical connector back on the way you took it off there's a very good chance your no pump is scrap weight. I have had plenty of new parts come out the box bad. But we always drive our selves nuts swearing it can't be bad we just put it in.

 

[Meltd0wn]

I'm leaning that way, tothemax. A pressure gauge is needed. BUT BUT BUT, don't they bench test the pumps before selling them?!! LOL!

 

[Awenta]

I'm leaning that way, tothemax. A pressure gauge is needed. BUT BUT BUT, don't they bench test the pumps before selling them?!! LOL!

That would make it used!

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[Meltd0wn]

That would make it used!

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:thumb:

 

[02greysixer]

A reputable Bosch rebuilt pump goes through a rigorous bench test before it is sold. Who knows what Pensacola does. If it's anything like their injectors they probably just pull out a core, slap some paint on it and ship it. Did your recently new injectors come from Pensacola as well?

Also, IF the pump is working and you connect your gauge directly to the outlet there's a good chance you're going to blow the gauge or hose apart. With the gauge hooked up instead of the line supplying the rest of the high pressure system the ecm is going to see 0 psi from the rail pressure sensor. It is then going to command the fuel pressure regulator to max flow. Being that the fuel will have nowhere to go and the ecm has no idea what you've done I wouldn't be surprised if you spiked over 10k psi very fast. Unless the pump is wasted.

 

[Brent@LDS]

X2^^

 

[Meltd0wn]

A reputable Bosch rebuilt pump goes through a rigorous bench test before it is sold. Who knows what Pensacola does. If it's anything like their injectors they probably just pull out a core, slap some paint on it and ship it. Did your recently new injectors come from Pensacola as well?

Also, IF the pump is working and you connect your gauge directly to the outlet there's a good chance you're going to blow the gauge or hose apart. With the gauge hooked up instead of the line supplying the rest of the high pressure system the ecm is going to see 0 psi from the rail pressure sensor. It is then going to command the fuel pressure regulator to max flow. Being that the fuel will have nowhere to go and the ecm has no idea what you've done I wouldn't be surprised if you spiked over 10k psi very fast. Unless the pump is wasted.

I finally put a pressure gauge directly onto the discharge port of this pump and it puts out no pressure at all. A bit of fuel comes out of the relief port, and the gear is not spinning around the pump shaft. I marked the gear, the shaft, and the nut with a sharpie, and that line doesn't budge.

Yes, I used pensacola injectors, and they solved the smoking problem. I'm not sure why anyone would paint an injector, lol. I drove the truck for a month with the new injectors and then decided to do the pump. The gauge I used is a 0 psi to 10,000 psi unit. I brazed a fitting onto an old fuel line and didn't worry about blowing it apart. If it came apart, I'd know I have plenty of pressure. The gauge didn't budge, so that's the problem.

 

[LBZ]

If your getting flow out of the pump but no pressure it's hooped. Seen it before on a supposed reman for an LBZ. Took the outlet line right off and it would pump fuel but you could hold your finger over the end.

 

[Meltd0wn]

If your getting flow out of the pump but no pressure it's hooped. Seen it before on a supposed reman for an LBZ. Took the outlet line right off and it would pump fuel but you could hold your finger over the end.

I just hooked up a clear hose directly to the outlet and cranked it over. I have fuel flow, but just about no pressure. It's a hooped rebuild, and I'm a bit pissed off. With what I'm gonna have to go through to get that pump back out again, I'm angryyyyyyyyyyyy

 

[Huffy67]

Yeah why anyone would buy anything from Pensacola diesel is beyond me. If 5 minutes of Internet searching doesn't make you wanna run away screaming idk what will.... Oh wait, having to replace a cp3 twice might do the trick!!! Hope you haven't forgotten how to replace those injectors either, doubt they last long at all.


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