Starting Problem => Which "fuel pump" to replace?

Discussion in 'Dodge Charger SRT8 General Discussion' started by Davin6.1, Oct 24, 2017.

  1. Davin6.1

    Davin6.1 New Member

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    So I've been having a starting issue for weeks now where the car won't start on first, second, third try etc. It's not an electrical issue and I discovered that if I cycle the car on and off a few times (assumedly to prime the fuel line) I get much better results. Often the car will start, run for a second and die but once it is running it runs like a champ with no fuel delivery problems. So I'm trying to tell if I need to replace the fuel pump itself of the other side which I understand is some kind of filter/regulator type combo. Does anyone have experience or good advise on this? Thanks!
     
  2. djalbin

    djalbin Active Member

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    Fuel enters the reservoir of the main fuel pump module (driver side). The main fuel pump module pumps the fuel through a filter, at the bottom of the main fuel pump, to the auxiliary fuel pump module (passenger side) through a supply line inside the fuel tank. The fuel pressure regulator inside the auxiliary fuel pump module regulates the pressure at 58 psi (± 5 psi) and sends fuel to the engine. Fuel that is not sent to the engine is returned back to the main fuel pump.
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  3. Davin6.1

    Davin6.1 New Member

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    That's good information, thanks! Do you know if pressure is maintained (after engine off) in the line between the secondary and engine (fuel rails) or if pressure is released? I'm guessing from what you're saying that my most likely issue might be a fuel pressure regulator that's on its way out. Would you agree?
     
  4. djalbin

    djalbin Active Member

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    The fuel system is under constant high pressure even with the engine off. It's possible the fuel regulator is not holding pressure (leaking down) when the engine is off.
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  5. Davin6.1

    Davin6.1 New Member

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    That's great information, thanks. That validates my working theory but I didn't want to pull the trigger on expensive parts till I confirmed that it actually works that way. My Haynes manual says that you can replace the regulator separately but of course when I went looking you can't buy that part separately anywhere. Thanks so much for taking the time to respond.
     
  6. djalbin

    djalbin Active Member

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    The Dodge Service Manual also shows the fuel pressure regulator as a serviceable part (i.e. can be replaced separate from the fuel pump), but this may have been the earlier Dodge Magnum models. I'm not sure if this serviceable fuel pressure regulator was in the earlier Dodge Charger models.
    In later Dodge Charger models the fuel pressure regulator is integrated with the auxiliary fuel pump module and is not serviced separately. The auxiliary fuel pump module must be replaced if the fuel pressure regulator is to be replaced.
    Fuel level sensor cards in the fuel pumps use to be serviceable too and now the fuel level sensors are integrated with the fuel pumps.
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    Last edited: Oct 27, 2017
  7. Davin6.1

    Davin6.1 New Member

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    Cool. Picked one up yesterday from my dealer for $140. Seems like a decent price from what I've seen out there
     
  8. Davin6.1

    Davin6.1 New Member

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    Well crap. I replaced the assembly today and at first it seemed like it might have worked but the last two times I have tried to start it does the same thing. Ugh. I'm about out of ideas. I don't see any place on the fuel rails where I can put a gauge to test the resting pressure. I've updated by signature to help with troubleshooting. There is fuel like discoloration around the upping intake gasket but it's an old car and I don't see any clear leaks around the injectors. I changed the spark plugs out around 10K miles ago. Frustrating...
     
  9. djalbin

    djalbin Active Member

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    You have to install a adapter kit to attach a fuel pressure gauge. You have to install it between the fuel line and the fuel rail. Your signature shows you have a DiabloSport Trinity. Connect it to the car's OBD2 port and look at the real-time fuel pressure readings. Standard OBD2 PIDs include Fuel Pressure (PID 10) and Fuel Rail Pressure (PID 34). PID 10 is gauge pressure. PID 34 is relative to manifold vacuum.
    There's also Fuel Rail Pressure (PID 35). It's also gauge pressure but it's only supported on diesel and gasoline direct injection engines.
    .
     
  10. Davin6.1

    Davin6.1 New Member

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    I've tried and I can't seem to find a parameter for logging fuel pressure in my Trinity. I've been reading forums but they are not much help so far. Here is what is available:
    2007-up PIDS


    Igntion
    Base Spark
    Deg
    Actual Spark Cyl 1
    Deg
    Intake
    Intake Air Temp Deg
    F
    Manifold Air Pressure
    kPa
    Barometric Pressure
    in Hg
    Injector Pulse Width Cylinder 1
    us
    Fuel
    REQD FUEL CHARGE CYL1
    mg/charge
    Miscellaneous
    1/1 Short Term ADAP
    %
    2/1 Short Term ADAP
    %
    2/1 Long Term ADAP
    %
    1/1 Long Term ADAP
    %
    DESIRED FA CYL1
    FAR
    OPEN LOOP FA
    FAR
    READ MAP KPA
    kPa
    P-Ratio MAP/BARO
    PRatio
    Misfire
    KNK LT RETARD
    deg
    KNK ST RETARD
    Deg
    Performance
    Vehicle Speed
    mph
    Engine Speed
    rpm
    Read Engine RPM
    rpm
    Throttle
    Throttle Position Sensor Percent
    %
    Accelerator Pedal Position
    %
    Throttle Blade Position
    %
     
  11. djalbin

    djalbin Active Member

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    It's difficult to tell without the corresponding PID #. Some of the parameters match the Standard list (e.g. Accelerator Pedal Position) but others may be manufacturer specific (aka ... Non-Standard). The majority of all OBD-II PIDs in use are non-standard. Does the Trinity data logging feature allow you to add PIDs to the parameters that are collected? With the the inTune i2 you can add PIDs to the default list of parameters collected during data logging.
    .
     
  12. Davin6.1

    Davin6.1 New Member

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    Trying to figure it out. The documentation isn't so great...
     
  13. Davin6.1

    Davin6.1 New Member

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    Well, so far as I can tell I can't add PIDS. In fact it seems that the only PIDS that are logged are the ones there are gauge monitors crafted for in a dash screen. Further, even though the unit is still getting power, Trinity won't log unless the engine is already started and it stops logging immediately if the key leaves run position. On a plus note, I'm not ready to say the issue has gone away as it has occurred a few times over the last few days but it does seem to be better. More good starts than bad starts so perhaps the PCM had to relearn some parameters of something of that nature. Still wishing the trinity did more but between the Manual and forum I am not getting very far. It may be that it just is what it is, cool tool for loading tunes and monitoring gauges but not much else. I can't even find a way to read the parameters on the built in tunes.
     
  14. djalbin

    djalbin Active Member

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    I have the Diablo i2. It only does data logging. You then upload the log files to your computer and view them using the DiabloSport Data Viewer. There's a default set of PIDs that are logged. I have seen the menu for adding PIDs but I can't access it currently because the i2 has a "please wait" hang condition when Data Logging (DiabloSport is working on the problem).
    If the Trinity has data logging, you might try going to those menus and see what PIDs can be added. On the i2 the Data Logging menu is included with the Scan Tool menus.
    .
     
  15. Davin6.1

    Davin6.1 New Member

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    Ok thanks, I'll check that. After a week or so now I can definitly say that the problem is better but still there which I think should be some kind of clue. It happened every time before and now it is only about 30-40% of the time. Not sure what that means though.
     
  16. Davin6.1

    Davin6.1 New Member

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    Jackpot! I guess with the Trinity, you have to have the Trinity plugged into the ODBII and then the laptop plugged into the Trin, and then the dataviewer will show you the other options. There are tons of them. Didn't see any of the ones you listed above. Here are three screen shots of the fuel PIDS available, any thoughts?
    [​IMG]
    [​IMG]
    [​IMG]
     
  17. djalbin

    djalbin Active Member

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    You may have to live with selecting the PIDs supported by the Trinity. But the playback of the data may reveal what's causing the delay in fuel delivery at start-up. You may have to do some searching to find information on some of the PID definitions. For example, "Fuel System Status" indicates whether the fuel system is in open loop or closed loop mode.
    .
     

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