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Loosing fuel rail pressure while driving

 
kdxkent
New User
Posts: 4
Joined: 03/10
Posted: 03/19/10 04:16 PM

This is not a Injector problem this time, nor is it the Fuel Regulator on the CP3 Pump nor is it the filter. I have put all new... Now this is the test that i have done several times: With a TECH II connected (in park) watching the fuel pressure desired and actual, it is fine up to about 15k then any desired above that it will not build. Now DRIVING with the tech II connected: As the Desired goes up past 13.5k for rail psi, the actual will drop to 3k or so and the truck has NO POWER!!! be fore I put a CP3 Pump on it can anyone tell me what else to check?  

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theSLEEPER.
Guru
Posts: 1748
Joined: 04/08
Posted: 03/19/10 05:22 PM

Low pressure fuel? I'm not too saavy with the common rail stuff yet, but have you tested the fuel pumps output? If so, I'd consider swapping the CP3 with a known good one and seeing if that solves the problem.  
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MarineOne
Addict
Posts: 2070
Joined: 10/08
Posted: 03/20/10 03:26 AM

Check your fuel rail pressure relief valve.  Its probably gone bad and releasing pressure before it's supposed to and would cause your problem.



Kris  

2006 Dodge Ram 2500 QC 5.9L - Smarty CR S-06 on SW #5

2008 Dodge Ram 3500 QC 6.7L - H&S MiniMaxx on DPF tune for towing
Titan Fuel Tank
Aero Muffler 4040XL
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kdxkent
New User
Posts: 4
Joined: 03/10
Posted: 03/21/10 10:14 AM

Swpping out the CP3 is just what I DONT want to do...about 8hours labor and around a $1000 just to swap it out!!! Any other suggestions?  

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theSLEEPER.
Guru
Posts: 1748
Joined: 04/08
Posted: 03/21/10 04:55 PM

Gotcha. Sorry, wish I could be more help. Check out that relief valve that MarineOne is talking about.  
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kdxkent
New User
Posts: 4
Joined: 03/10
Posted: 03/23/10 02:45 AM

The FPRV is fine. Shimmed it yesterday and it still will not build anymore pressure!! Guess the pump is next.?.?.?  

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MarineOne
Addict
Posts: 2070
Joined: 10/08
Posted: 03/23/10 05:20 AM

How about the lift pump?  Have you checked to make sure it's giving you at least 8 psi?

Any air in the fuel?  Checked all the fuel lines from tank to filter?


Let's do the small stuff first before we assume it's the CP3.




Kris  

2006 Dodge Ram 2500 QC 5.9L - Smarty CR S-06 on SW #5

2008 Dodge Ram 3500 QC 6.7L - H&S MiniMaxx on DPF tune for towing
Titan Fuel Tank
Aero Muffler 4040XL
Nathan AirChime K3LA

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Richies Truck and Auto
Enthusiast
Posts: 362
Joined: 05/08
Posted: 04/16/10 10:27 AM

Hey kdxkent, are you running stock tune? You stated you replaced the "fuel regulator" on the CP3? Which are you referring to the cascade valve, the FCA??? I would verify you are receiving 100% duty cycle on the FCA where required in addition to checking your fuel delivery rate on the low side.  
Rich
05 GMC 3500HD CC/LB LLY
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