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Thread: Loss of rail pressure and P1223 code, Tuning issue?

  1. #1
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    Default Loss of rail pressure and P1223 code, Tuning issue?

    Hi, I am chasing a loss of rail pressure under load and an associated P1223 code( unknown leak detection based on quantity balance). From my understanding, the ECM sets the P1223 code when calculated fuel flow exceeds an expected value. I/we have checked all the mechanical parts, lift pump, cp3 pump, FCA, PRV, connector tubes, injectors, etc and I still lose rail pressure under load. My question is, are there parameters in a tune that can cause the truck to lose rail pressure. Too aggressive a tune or something along those lines? I am fairly clueless on tuning and trying to get up to speed so I can diagnose this problem. No one can seem to find the problem and I could really use some insight.

    Thanks Lebo

  2. #2
    Senior Member tylerltr450's Avatar
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    Having an aggressive tune and not enough pump can cause this drop in rail pressure. FCA going bad can cause rail to lose pressure in load. a Data log or tune file is a major help.

    Also what are your mods, how did you check your CP3 to determine if it can handle the 28000 PSI pressure?
    2006 Cummins Red, Auto to Nv5600, SBC 3600, Traction Bars, Visor, Running Lights, S&B Intake, ATS intake horn, EFI Live, Borg Warner S363 Turbo, Industrial Injection Dragon Fly Injectors.

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    Thanks a lot for the reply. I have new BBI stage one injectors, a built transmission, FASS 150, Edge CTS2, and EFI Live. Replaced FCA, and PRV. Ruled out the CP3 by swapping with another CP3, swapped the rail, basically everything mechanically that they could think of related to the fuel system. Since, nothing mechanically is proving to be the problem, I thought maybe it could be tune or ECM related. I asked the shop to put a stock tune back on the truck but I still lose rail pressure. I'd like to know how to tell what is actually on the ECM. Are the parameters really stock or is the ECM stuck on an older more aggressive tune? How could I provide you with that information? Right now, all I have is an autocal.

    I did not know it before adding EFI live but I found out the previous owner had a Smarty on the truck. I have since read that an EFI live tune over a Smarty can cause problems if it isn't returned to stock before adding the EFI Live tune. I did not write or flash the truck so I don't know how it was done. Is it feasible/realistic that some or part of the tune is being blocked by the Smarty? Also, this may just be a coincidence but my fuel gauge is not accurate after the return to stock flash. Reads 1/4 tank after driving 60 miles on a full tank. From my understanding, I can't get access to the tune file since I didn't make it or have a V2. Any guidance is greatly appreciated. Let me know what I can do to help you help me. I have a truck that I have spent a ton of money on, and now I can't use it to tow without getting a P1223 code every 10 minutes. The loss of rail pressure is the problem. The 1223 code is just letting me know I have the problem. Thanks again. Lebo

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    Where are you located at?

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    Senior Member tylerltr450's Avatar
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    Where are your data logs? and if you didnt tune the truck have you been working with the tuner?

    Trucks should always be flashed to stock before a tune is dropped in. OS could be an issue if the tuner used an incorrect version.
    Last edited by tylerltr450; November 27th, 2019 at 04:12 AM.
    2006 Cummins Red, Auto to Nv5600, SBC 3600, Traction Bars, Visor, Running Lights, S&B Intake, ATS intake horn, EFI Live, Borg Warner S363 Turbo, Industrial Injection Dragon Fly Injectors.

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    twildman, I am west of Fort Worth Texas.

    tylertr450, I tried to data log yesterday. Autocal allowed two logs but when I tried to do more it would go straight to saving the log without recording. Thinking maybe the autocal only allows very limited logging. I apologize, I am trying to learn this stuff as I go. I need to find some more YouTube videos to watch and figure it out. I am assuming I need an PC or a MacBook with with bootcamp to run windows so I can upload the files?

    I didn't got direct to a tuner. The shop I take my truck to got the tune from a tuner and loaded it. Truck drives like it has a tune on it but shop owner flashed it back with the latest Chrysler flash. My rail pressure at idle is around 7400. Thought that was a little high for a stock tune. But I don't know.

    Also, one thing I should have mentioned was the shop told me that the rail pressure issue is still present when he pulled the fuel control actuator (which should take the ECM out of the equation).
    I don't know, I drove it yesterday without a trailer and I got the P1223 code about 6 times in an hour of driving. Sucks, I can't figure it out. 2 shops so far and no luck.

  7. #7
    Senior Member KhakiCummins's Avatar
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    When did this issue start? Was it after the BBI install? It could be one or more of the cross tubes for the injectors are not seated properly and bypassing fuel.

    7400 PSI at idle does sound high. On a stock tune, idle should be around 5000 PSI. I have not seen idle that high on any of the modified tunes that I have either but I suppose everyone writes tunes differently.

    I have never heard of anyone having issues flashing a new tune over a Smarty tune with EFILive. EFILive does a complete re-write of the ECM so it would over write whatever Smarty Tune is in there. Even when returning to "stock" with a Smarty, it has been shown that the resulting tune in the ECM is not really stock as it does not do a complete write of the ECM. This caused issues with some folks bricking ECMs early on when EFILive started supporting the Cummins tuning. EFILive now performs some checks and won't let you write a file with Check Sum errors like those that are found when using a Smarty "stock" file as a tuning base.
    Duane

    2008 Ram 3500 QuadCab
    Hamilton 110# Springs & HD Pushrods, ARP 2000s, EFILive, SB 3250 DD

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    I often run idle rail around 6500-7000 on stock trucks, and up to around 10,000 on big injector trucks.

    I also agree it could certainly be an issue with cross over tubes. Do a fuel return test and see what's going on. If your truck is idling aroudn 7400 with a stock tune it's likely it's returning a lot and having to push into the tune a little further (More MM3 commanded) which could put it into a place on the map where rail is elevated.
    06 SCLB. Built 48re, ATS Twin cp3, 369sxe, Fass 220, Hamilton 188/220, 110# springs, 100% over's, ARP 625's, Big valve head, .40 over, 12v rods, balanced rotating assembly. etc..
    Tenacity Tuning
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