I need some help on my 02 LB7 I just had new injectors installed and new fuel filter and new LBZ CP3 with modded fpr and my rail pressure is 9800 psi and drops to 600 psi when going to wot? I dropped out fuel tank tonight to see if pickup screen was blocked and it was clean. Truck is very slow to accelerate. Starts right up no smoke or missing, no codes, rechecked all cp3 lines to make sure they were tight. No fuel smell, no fuel in oil, full of coolant. I am at a complete loss, any suggestions or ideas on what to look for. Thanks for any info!!!
LB7 Low Fuel Rail Pressure
- Thread starter 02 DMax
- Start date
If it's a mod'd reg.. I'd say that the plunger is sticking in the bore. Pull it out if you have a chance and bang it against your palm.. If you can't hear the armature banging around then it's stuck. That's the dodge approved method of FCA testing 
Low Rail Pressure?
I installed the cp3 myself. Can the fpr be removed without pullin the entire cp3 back out? I bought a new Lb7 regulator and had that modded.
I installed the cp3 myself. Can the fpr be removed without pullin the entire cp3 back out? I bought a new Lb7 regulator and had that modded.
i talked to 02 dmax (rick) on the phone and he was having this problem before he installed the modded cp3. the low pressure was the reason for the injector change and the new cp3. i thought that kind of ruled out it being a tunning issue especially since he is running a ppe and it was doing it with the stock cp3. he also told me that a gm diesel tech used a tech2 and that the truck was only commanding 128 mma at full throttle. i sent him here to try to get this figured out. thanks for the help guys
Rail Pressure
What would happen if i unplug the fpr electrical connector and start the truck, i should hear different tone from the motor? Maybe or is this a bad idea?
What would happen if i unplug the fpr electrical connector and start the truck, i should hear different tone from the motor? Maybe or is this a bad idea?
Ya if you unplug it you should definately notice whether or not your pumping some good rail pressure.
Low Rail Pressure?
Where is the relief valve on the junction block located on my lb7? I have had two people tell me shim this up by adding two more shims and put it back together.
Where is the relief valve on the junction block located on my lb7? I have had two people tell me shim this up by adding two more shims and put it back together.
The relief valve is located on the Y bridge.....I didnt know you could shim them? I just removed the valve and plugged it off
I agree with Brayden on the regulator sticking,you dont have to remove the cp3 to get it out either
It ont hurt to unplug the regulator,And YES it should max out the current on it and make it sound very loud.....if it doesnt then it's probably the valve stuck
there is also a way to check the current,But I suck at electrical stuff
Low Rail Pressure?
Thanks for the info!!! i am going to reinstall the fuel tank tonight and try unplug the fpr and maybe i will just pull the fpr and is there anyway to check to see if it is stuck?
Thanks for the info!!! i am going to reinstall the fuel tank tonight and try unplug the fpr and maybe i will just pull the fpr and is there anyway to check to see if it is stuck?
bang it on your palm.. if you can't hear it moving it's likely stuck..
Try pulling the connector only first then restart the truck.. Rail pressure should climb to 23,000 -26,000 due to no current @ the solenoid. If it does then it's not the solenoid.
Brayden
Try pulling the connector only first then restart the truck.. Rail pressure should climb to 23,000 -26,000 due to no current @ the solenoid. If it does then it's not the solenoid.
Brayden
Low Rail Pressure?
Ok guys i had a brain fart, while watching my rail pressure the desired pressure would only go up to 9800psi on the 120hp setting on my ppe hot +2 and the actual was 1600 psi. I think i have a electrical problem. I am going to remove chip and install on my 01 and check rail pressure on that truck, i know it worked fine on this truck before for the last three months. Does the box on the pass side valve cover control rail pressure? IF so would the box from my 01 work on my 02? The command pressure never went above 9800 psi. I feel bad for not catching this earlier.
Ok guys i had a brain fart, while watching my rail pressure the desired pressure would only go up to 9800psi on the 120hp setting on my ppe hot +2 and the actual was 1600 psi. I think i have a electrical problem. I am going to remove chip and install on my 01 and check rail pressure on that truck, i know it worked fine on this truck before for the last three months. Does the box on the pass side valve cover control rail pressure? IF so would the box from my 01 work on my 02? The command pressure never went above 9800 psi. I feel bad for not catching this earlier.
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Low Power?
I put tank back in tonight and left shop and truck run great instant boost and that lasted short time and back to old turd again. So i went back and unplugged fpr and it took a few seconds then it sounded like timing was advanced while idleing. Should it still idle smooth with fpr unplugged or will it run rough? So i am going to pull fpr friday night and smash it and buy another modded one and try that. If that doesn't fix it any other ideas besides getting rid of truck and start over on another one, maybe different brand?
I put tank back in tonight and left shop and truck run great instant boost and that lasted short time and back to old turd again. So i went back and unplugged fpr and it took a few seconds then it sounded like timing was advanced while idleing. Should it still idle smooth with fpr unplugged or will it run rough? So i am going to pull fpr friday night and smash it and buy another modded one and try that. If that doesn't fix it any other ideas besides getting rid of truck and start over on another one, maybe different brand?
If you unpluged it and it rattled like it had really high pressure then its working. You got problems else where
That box is the FICM the rail pressure is controlled by the FRPCV on the CP3. Take the programmer out for all diagnostics. The FICM and FRPCV should be interchangeable between the two years.
With a tech II check command verses actual pressure and do the unplug default and see if pressure max's out as described.
Fuel pressure
Thats what i needed to know, yes it sounded like high timing with the fpr unpluged. So there is no sense in removing that? I will get hooked up to tech II and see what that says and hollar back. I will hook up vacuum gauge to test port and check that again also.
Thats what i needed to know, yes it sounded like high timing with the fpr unpluged. So there is no sense in removing that? I will get hooked up to tech II and see what that says and hollar back. I will hook up vacuum gauge to test port and check that again also.