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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

    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:

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

    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?

  2. Avatar


  3. Boydie

    Boydie S3 8V DSG VCDS Map User

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

    Here tomorrow
    Last edited: Jul 31, 2020 at 9:31 AM
  4. Peter82

    Peter82 Active Member

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

    Boydie S3 8V DSG VCDS Map User

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


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