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Possible Low Fuel Pressure?

Discussion in '06-07 LLY/LBZ' started by Mad Maxx, May 8, 2008.

  1. Mad Maxx

    Mad Maxx See, what had happened was... Staff Member Moderator

    5,995
    118
    May 3, 2008
    Long Island, NY
    I decided to plug in my PPE Tuner and check out the Real Time Parameters of my Truck, then I started looking at the Desired & Actual Fuel Pressures.

    So I went for a drive and monitored the Pressures.

    I'm running the PPE on Level 6, so it is Commanding 26,000psi but I am only getting 23,xxxpsi. I have TTS Dual Lift Pumps.

    Does this seem right, or is it a little low for having Dual Lift Pumps?? Fuel Filter has maybe 1000-1500 miles on it.
     
  2. BKDespain

    BKDespain Recruit

    184
    0
    May 8, 2008
    Utah
    Can you turn the flow up from the lift pumps? It could be that simple. FPRV could have went bad, if so, get PPE's shim kit or race valve for the fuel rail. LVL 6 pulls a lot of fuel.
     
  3. Mad Maxx

    Mad Maxx See, what had happened was... Staff Member Moderator

    5,995
    118
    May 3, 2008
    Long Island, NY
    Nope, as far as I know, the TTS Pumps "are what they are" they are not adjustable.

    I've never thrown a CEL for anything Fuel related. Only EGR, but that was for obvious reasons at the time.
     
  4. Mad Maxx

    Mad Maxx See, what had happened was... Staff Member Moderator

    5,995
    118
    May 3, 2008
    Long Island, NY
    Does anyone know the GPH or PSI of the TTS Duals? It's not listed on their site, just says it's good to 600 Wheel HP.

    Surely I can't be over that with just the mods. listed in my Sig. right? Even I would find it hard to believe if I was.
     
  5. Diesel Tech

    Diesel Tech Registered User

    98
    0
    May 8, 2008
    IF your desired fuel pressure and actual pressure vary there could be several reasons for it. The first thing you need to do is drive around and try to keep the engine steady. If it holds the proper pressure then it's not a supply issue. The ECM will only adjust the pressure in slow steps so if it's not correcting fast enough during a quick acceleration it's a code issue not a supply issue. Most LBZ have not had an issue with the relief valve but that is possible but not likely in your case.
     
  6. Mad Maxx

    Mad Maxx See, what had happened was... Staff Member Moderator

    5,995
    118
    May 3, 2008
    Long Island, NY
    Yea, I was monitoring it while just driving normal also, and it was spot on. But once I come out of a stop and I hit 3rd & 4th, getting into the taller gears, its commanding 26,000 but I'm only getting 23,xxx. I doesn't go lower or higher than 23,xxx. Just fluctuates within that range.

    It's pouring here right now, so I can't really check anything on the truck.

    I gotta get under the Truck and have someone else in the Cab and turn the Key to ON. TTS says the LP's have a 2 second Prime whenever the key is turned, and either the LP's are REALLY quiet, or they aren't working, because I can't hear them prime when I sit in the Cab and turn the Key.

    They are a flow through design if they happen to crap out, but can the Stock Fuel system supply 23,xxx without the help of a Lift Pump?
     
  7. Mad Maxx

    Mad Maxx See, what had happened was... Staff Member Moderator

    5,995
    118
    May 3, 2008
    Long Island, NY
    Got under the truck today and the LP's are working. I could hear 'em and felt them prime when the Key is turned. So they are working.
     
  8. Diesel Tech

    Diesel Tech Registered User

    98
    0
    May 8, 2008
    James

    More than likely it's in the code in the ECM. The program is not correcting the CP3 quick enough when the pressure is falling under heavy loads. Industrial Injection has a modified CP3 that reacts quicker than a stock one or you can look around the net and find the DYI modification for the regulator that may solve your issue.
     
  9. tomrex

    tomrex Professional Idiot

    Any chance of a stuffed up filter? Mine starts slowly dropping when it starts to plug. Mine doesn't have lift pumps, but I figured I'd drop the idea. Just a thought. :)
     
  10. Mad Maxx

    Mad Maxx See, what had happened was... Staff Member Moderator

    5,995
    118
    May 3, 2008
    Long Island, NY
    No, Fuel at the Station I get from is clean. Only have about 1000-1500mi on current filter.
     
  11. BKDespain

    BKDespain Recruit

    184
    0
    May 8, 2008
    Utah
    I would pull the filters out of the pumps and clean them, maybe the pressure will come back. Is the trucks performance getting worse? The same or just noticed pressure was down? Maybe try pulling the filters and running without them.
     
  12. Mad Maxx

    Mad Maxx See, what had happened was... Staff Member Moderator

    5,995
    118
    May 3, 2008
    Long Island, NY
    As far as I know, TTS Pumps don't have filters in them.

    Trucks performance is the same, just decided to plug in the PPE that day and see what was going on and check things out, never did it before.

    I would never run the truck without a Fuel filter, no matter how clean the Fuel is in my area.
     
  13. stacks04

    stacks04 McLovin

    3,579
    0
    May 9, 2008
    terryville ct
    your pump might just be weak and not capable of holding the 180mpa that it is requiring. just for soots and giggles take out the ppe and load the stocker in it. see if it holds then. if it does then you know your asking for to much fuel and it cant maintain the desired. then you know you need to look into the pump mods.
     
  14. dmaxx3500

    dmaxx3500 Deputy

    3,204
    3
    May 3, 2008
    chicago,
    i had a gm filter on for 1 year ,then i changed it and this one didn't last 1 month,milage doesen't matter
     

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