Injector regulator on a LB7
 

For testing, What should I see if the regular is unplugged. I think it is bad so I am looking for ways to troubleshoot it????? Anyone have a suggestion?

if you unplug the regulator the rail pressure should jump up to 23kpsi

And if the regulator is bad... Then it should drop or stay the same at a low pressure?

160k on the truck the pump could be bad, but the regulator can have trash in it, if you have time you can pull it out and clean it up but its a tedious job to take apart a regulator

I am taking one off a friends truck and gonna try it on mine today. Wish me luck the problem is the regulator and not the PUMP!!!! Ill save $500 bucks if the regulator fixes it!!!! Ill let you know what i come up with...

---AutoMerged DoublePost---

:dixie:

Well it did not fix it. But it seems to be better. I am going to check everything again with the Tech II again and see if it's getting the pressure that it asks for.:td:

:pca1:

Okay, I checked it again with a Tech II and the same result. :ouch: Okay...I have just yesterday put a Regulator on the CP3 pump. (Took about 1 1/2 hours) What else is there to check? What about the valve at the end of the fuel rail on the drivers side? What is it called and how can I check it?or would it even be a possibility that it might be dropping the pressure. Again now this is the testing that I have done: With the Tech II connected, IN park it will build up to around 15000psi. Then driving: when desired reaches 17k 18k 20k, and higher the actual will drop to 3k or so... Am I missing anything before I spend the money and the time to put a new reman CP3 pump on it? Somebody help a fella out!!!!! :scare2:

The valve your thinking of is the fuel rail pressure relief valve, and on the lb7's its on on the back of the rail, its on the fuel junction block.

https://www.dieselbombers.com/lb7-bo...-shim-mod.html

What do you think is the problem and how can I check the relief valve at the back of the rail?

---AutoMerged DoublePost---

I read your write up on the leak LB7 FPRV and seen the pics thanks for that!!! But do you think I am loosing the pressure on the rails threw the FPRV or do you think the pump can build 15k psi and then just drop all the way to 3k psi all at once. I just have never seen a pump build that kind of pressure and all the sudden drop like that. and if I watch the Tech II real close, when I let off the peddle the pressure will jump up from 3k to like 15k and then back down to the desired psi. I really need some help on this. I dont want to do all that work and spend all the money to replace the pump and it be something like the FPRV. Should I cap it off or just ad the washers to it?

what are all the simptums you are having?

Well it started with no power after mid throttle to the floor. I have replaced all the small stuff, filters and even the fuel regulator on the pump but still no change. With a Tech II connected driving it will drop from 15k psi to 3k and then when I let off the throttle it will jump back up to about 15k and then down to desired.

first I would check and see if you have a fuel line colapsing in or out of the fuel filter. If you have a way to check fuel pres. check the actual with the engine off it should read 1.1 to 1.8 mpa, if not your pres. sensor could be bad. I have an lly and am not sure how the lb7 are set up but if you take the line off between the fuel rail and the return, plug the return side and start the truck if you have fuel coming out the fprv it is sticking open. and for the regulator there should be a way to go in with the tech II and graph out what the desired is and what the actual is.

I have been told that when the pump starts going bad it just GOES, and the symptoms that I am having are not for sure the pump. So I am trying to get help with the trouble shooting of the FPRV. The leak earlier sort of confused me. I think the FPRV is on the backend of the rail on the drivers side but the lics show that it is located above the CP3 area just to the right side of center.?.?.?

---AutoMerged DoublePost---

Yes I have checked the hoses from the filter. Used a vacume gauge to test this. All checks good on the input to the pump. Can a pump just drop from 15k to 3k and always at the same pressure?

---AutoMerged DoublePost---

It really seems that the FRPV could be popping off at 15k or so and causing this...???

what year is your truck

---AutoMerged DoublePost---

I have an o5 lly and the fprv is at the back of the ds rail there is a rubber hose going from the fuel rail to the return line if you pull the rubber hose of the fuel rail and plug it so you dont loose fuel from the return. then put another hose on the fuel rail run that into a pop bottle or somthing. Start the truck and if you get any fuel in the pop bottle the fprv is not sealing up. the fprv should not open until just 23000 psi.

Okay, at the end of the fuel rail the FPRV has a metal line connected to it and it comes back up to something that has several lines connected to it. There is a Banjo bolt that this metal line goes to and there is a rubber hose there. Is that where I can plug the return and put a hose in a bottle?

---AutoMerged DoublePost---

oh it is a 2003 3500 dually

so the metal lines comes up to a distribution block and bolts to it and then there are rubber lines that also come into it correct

I think I may have been confused on what I was looking at. There is nothing other than a metal line running from the backend of the fuel rail. It runs back up to the middle of the motor up just above the CP3 area. I think I can see the pop off valve (FPRV) on left end of something? what is it screwed into?

The lb7's dont have that kinds of set up, thier fprv is located on the end of the junction block in the valley of the engine



The metal line is part of the supply for the injectors it coes from the juntion block to the fuel rail.

the little line with the banjo bolt is the fuel return line and thee return fuel from the cp3, injectors, fprv all share that same line.

to tell you the truth I am not sure what exactly it should look like on an lb7
Is there any way to take a picture of it

look at post #9

buy the way it looks you will have to pull the banjo bolt out and find a way to block the hole in the fitting(the t). I would say like a 3/8 bolt two washers and a nut and make a gasket out of like a piece of cardboard from the back of a noetbook to go between the washers and the fitting. Then put a piece of hose over the fprv like I said before, the hose will have to be pretty big like a 5/8 heater hose. that is what it looks like to me but if anyone else has a better idea giver a whirl

there is a way to test it, i just cant remember the steps ive only read up on how to test it on a lb7 once, but the amount of time it takes to get down there and test it just spen 5 more minutes and shim the darn thing

Okay while I was gone out in the garage working on this thang, You guys were trying to help me out. THANKS!!!! Now what I just did was I looked at that link on post 9 and went out to the truck and I found it. I pulled it off and shimmed it. Used 3 washers and put it back together and guess what?.?.?.?. IT STILL IS NOT BUILDING PRESSURE!!! Is there anything else it could be other than the PUMP?

what kind of pres. does it build when you are in park and rev it up. what kink of pres does it make at idle?

Read my post #8.

besides it being injectors it would be the pump being bad.

there could be a small chance of it leaking out under the injector lines that go in the valve covers, but you would also get diesel fuel in the oil as well. there is a test that can be done to see if that is happening is to jack up the rail pressure at idle and let it sit for 5 minutes and see if the oil has risen.

but other than that its pointing to the pump.

I dont know it will make the truck do what it is doing but my service manual says that one thing to check is that the fp senson is reading correct 1.1 to 1.8 mpa with the truck off

The only time this low pressure happens is when the desired goes above 14k to 15k and above...at that very time the actual drops to 3k or 4k psi and even sometimes gives a low pressure in fuel rail code. I dont remember the code number.

---AutoMerged DoublePost---

Well you have been with me from the start of this and I thank you for you help. You know everything I have tested and how...all the results and symptoms, you dont think I have missed anything do you? It just seems so odd that when to builds the 15k and then just drops off to 3k all at once.?.?.?

---AutoMerged DoublePost---

Oh and I just changed the oil and there is no fuel in the oil. 6 months ago dealer installed all 8 injectors.

---AutoMerged DoublePost---

Also just to let you know alittle more about this, it runs great as long as you dont get into the throttle like 1/2 peddle or more. That is about where the tech II shows the desired going over the 15K psi and higher.

I dont think it is the pump because the pump would just stop building pres not dump it like what is happening, unless it has somthing to do with throttle position sensor but you think it would throw a code. What year truck was the fpr you tried off of.

Well I was going to use one of my friends fpr but I decided against it nad just put a new one on it from Chevy Dealer...$350:scare2:

---AutoMerged DoublePost---

What else could it be? I have tried everything that anyone has come up with except the pump...

hmm :humm:

Humm...Well, let me know if you come up with anything else to check before I replaced the CP3.

OKay guys I have not yet pump a pump on the truck but I did disconnect the regulator to see what would happen. With it disconnected the motor would not rev over 2000rpms. I did not have a tech II with me to check pressure nor codes. But it would not rev over the 2000rpms. What is this telling me?:humm:

probably engine limp mode, the engine realizes that i cant make the rail pressure commanded and it goes into an engine limp to protect itself limiting you to 2000rpms

So disconnecting the regulator doesn't really tell me anything? I thot you had told me the pressure would go to 23000psi all the time if it was disconnected? And if it does, the electricly everthing is good? What if I disconnect the regulator and connect it to the old one and just lay it there, what shOuld I see then when I drive it? If n change the pump is forsure bad then?

inside the regulator is like a little solenoid, and when you disconnect it the spring inside it defaults it back to its max flow position, and if the pump is good (being that you have a brand new regulator) it will pump the maximum amount of fuel and ~23kpsi will be your pressure.

What is the link for the CP3 Fuel pump replacement that has the list of gaskets and everything I will need to go back together? I seen it one time before but I can not find it now that I need it.

I never actually did a complete write up on how to do it, but the stuff is still fresh in my head and i do have some pics in my photobucket.

http://s219.photobucket.com/albums/cc9/2500heavyduty/DIY/cp3%20replacement/
The password is "daniel"


The first 5 pics probaby help you the most when you get down to the cp3, you have to walk it out with two screwdrivers and then grab it from the bottom and roll it up and out.

idk why it gives you a video, just click the url on top of the box