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Help ! What's going on ?

Jefecito Sep 13, 2018

  1. Jefecito

    Jefecito Member Team Daytona TFSI Owners Group Audi RS3 Sportback S tronic

    Hello everyone,

    I own a PFL for pretty much a year now and the RS3 adventure is becoming a nightmare since yesterday.

    I was sitting in the car yesterday using VCDS and testing a few diagnostic softwares, and left the car idling for a long moment, probably 30 minutes +.

    I started progressively smelling fuel outside the car and discovered a leak behind the right hand tyre.
    The panic was real and I instantly shut off the engine. Not even understanding why I pulled the tank cap, hearing a big pressure release that progressively stopped the fuel leak.

    The leaking area I identified is basically the active charcoal container or right behind it.

    I brought a mechanic to my place and started the car again, but we couldn't reproduce the leak.

    Today I started the car I went for a very quick drive around my neighborhood :
    - driveability is atrocious, obvious loss of power, under regular load sometimes the car is jerky and I can clearly feel power cuts as engine RPM goes down then back up while the throttle is applied
    - idle feels super weird and not very regular, monitored it through vcds and discovered that I was going from low 700 (710) to almost 800 RPM at idle.
    - car can be left idling and engine shuts off by itself (happened twice)

    VCDS and other softs scan brings no error regarding engine/fuel system issues.

    What do you guys suspect ?

    Active charcoal container ? Fuel pump ? Fuel pressure regulator ? Purge valve ?

    Few additional data :
    Nothing under the hood, no leak and no fuel smell on the oil dipstick.
    Car is stock, only a few mods like secondary decats, nothing serious.
    Service less than 3000km ago, including new spark plugs.

    I live in a country where Audi don't even sell Petro A3s, let alone RS models. (all replacement items have to be ordered, it took them a month to bring 5 spark plugs)

    I just want to know what I'm up against before taking it there.

    Thanks for reading.
    Last edited: Sep 13, 2018
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  3. Hal Adams

    Hal Adams Active Member Team Nardo VCDS Map User Audi RS3 Black Edition

    First - when you open the cap, is there a pressure or vacuum release? It is important to know this. Pressure release is normal and I assume this is the case with you.

    Why would you want to leave the car idling for 30 minutes..? The RS3 engine delivers very high pressure to the fuel rail, more than most to cope with the high demand when is spirited driving mode. Sitting there for 30 minutes with this high pressure is, in my book anyway, not the best use of this engine!

    It sounds to me, and I quantify the word 'sounds', as if the fuel system is building up pressure from your excessive idling and maybe coupled to the ambient temperature (where do you live?) the tank pressure is at its limit and evaporate emission sensor is over worked, so it is just bunging the pressurised gas into the evap box that in turn is condensing into the leak you see.

    I hope as one of your mods, you do not have a high pressure pump?

    It further sounds to me that you have upset a sensor - maybe even the ees one - along the way that is now giving you extra problems. If you are not seeing anything on VCDS, then you need the next level. Dealer or good independant.
    Last edited: Sep 14, 2018
    AudiNutta likes this.
  4. Jefecito

    Jefecito Member Team Daytona TFSI Owners Group Audi RS3 Sportback S tronic

    Thanks for replying Hal.
    I believe it was a pressure release when I opened the gas cap.
    It might sound stupid but I had just received diag tools and I was testing a few things like data logs, live data monitoring and didn't realize the impact it would have on the car. It's definitely a mistake.

    Plus, I live in Morocco, if I remember it was 26 degrees Celsius when this happened.
    I don't have a HPFP.

    Until now I wasn't able to reproduce the leak to make sure it's from the active charcoal canister, do you think there's any other possible suspect leaking fuel in that area ? (behind the right hand rear wheel).

  5. Hal Adams

    Hal Adams Active Member Team Nardo VCDS Map User Audi RS3 Black Edition

    There are loads of pipes running in and out of the tank that are potential culprits. ~But if you cannot reproduce the leak, then it has to be a build up of high pressure gas condensing. I'd be more worried about the rough running you talk about - I am fine with mechanical logic, but when it comes to sensors, I have not a clue...

    I am a few degrees north of you snuggled in behind the Pyrenees and notice on hot days, even such as we are having now in the mid twenties, the pressure build up in the tank is quite significant comapred to winter days - sometimes the odd whiff but never experienced a leak.
  6. Jefecito

    Jefecito Member Team Daytona TFSI Owners Group Audi RS3 Sportback S tronic

    Thanks for your help Hal.
    Trying to contact the dealer to book it in.
  7. AudiNutta

    AudiNutta Well-Known Member Team Racing Blue Mica Audi RS3 quattro Sportback

    Good luck, hopefully they can get this sorted for you. I will keep an eye on this thread to see what you find.
  8. T-800

    T-800 Well-Known Member Team Glacier TFSI Owners Group VCDS Map User Audi RS3 quattro Sportback S tronic MQB Platform

    Could be that the active charcoal canister is on its way out...

    When I had the fuel pump cutting out issue the Audi Assistance guy explained that whilst the car is idling the lift pump in the tank is only getting a very small voltage and on some modules there was a software issue that would cause the voltage to drop to 0.0 thus cutting out the car.

    The point I’m making is the very low voltage ensures enough fuel being sent to the hpfp at the front to suit the idle conditions. Once you use the throttle the voltage climbs as it reads demand increase from throttle position.

    The only other place that I’ve seen leak is the HPFP sensor fitting, had it on my 8P where it stank of fuel although it’s not in the location you say your leak is.
  9. Jefecito

    Jefecito Member Team Daytona TFSI Owners Group Audi RS3 Sportback S tronic

    Thanks I'll update the thread when I'll have a feedback from the dealer.
    I was going to PM you as I read somewhere else that you had a FP issue on PFL.
    I think the active charcoal canister is dead anyway, I've read everywhere else that when liquid fuel gets inside the canister you need to replace it as it's made for fuel vapor.
    On the brighter side, I think that a leak located by the rear wheel sounds less "important" than something that would be closer to the engine bay.
    From my various readings online it could be anything from the EVAP system itself, to the fuel filter, purge valve, fuel pump, etc.

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