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PFL S3 - Start/Stop system fault leading to fuel rail/pump pressure low

Boydie Jul 31, 2020 at 9:17 AM

  1. Boydie

    Boydie S3 8V DSG VCDS Map User

    3,945
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    Hey guys

    Seems to be the first major fault with my 2014 S3 since ownership this last 3 years.

    Bit of info on my S3 in case you don't know or remember:

    2014
    47k miles
    Revo Stage 3+ (important: entire LPFP and HPFP internals changed around Oct 2018)
    Meticulously maintained
    etc...

    Just this last month, an "automatic start/stop: system fault! Function unavailable" notice comes up on the DIS.

    At the time, I went another drive, start/stop worked fine, turned off engine and on, etc... went away.

    Next time it happened, I drove up to a junction, engine stopped as normal but I immediately pressed accelerator to go, so the engine stopped momentarily and started again. Next thing, engine management light came on.

    Plugged on OBD11 and the following showed up on engine:
    • P008700 Fuel Rail/System Pressure too low
    • P308D00 Fuel Pump Engine Speed too low
    And this has been the case the last 3 times the light has come on. My theory is that because there is an issue with the start/stop, the car then thinks fuel pressure is too low hence the two above faults.

    Only seems to happen after the engine cuts off for start/stop and when I have it turned off manually, the engine light never comes on.

    So, on initial Dr.Google diagnosis there are a few things to check:
    • I have read about a sensor to do with start stop that could be faulty but I have no part number
    • Could be an issue with the cam follower (which I changed in Oct 18 for the HPFP internals)
    • Could be an internal cam shaft issue but IMO I don't think so as the car performs perfectly fine 70+ miles a day
    I think I will change my cam follower for peace of mind. Did this all the time on my 8P S3 as precaution.

    Any other suggestions or advice from previous experience?

    Thanks
     
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  3. Boydie

    Boydie S3 8V DSG VCDS Map User

    3,945
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    Just ordered a new cam follower to change for peace of mind

    06H109311
    £34.30
    Here tomorrow
     
    Last edited: Jul 31, 2020 at 9:31 AM
  4. Peter82

    Peter82 Active Member

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    Or maybe high pressure fuel pump needs replacing ?
     
  5. Boydie

    Boydie S3 8V DSG VCDS Map User

    3,945
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    @Peter82 who knows. The internals are Autotech so will see what it looks like when I have it off

    thanks
     

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