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PLEASE HELP - Possible faulty fuel pump / relay on S3??

Discussion in 'A3/S3 Forum (8L Chassis)' started by Az, Mar 9, 2012.

  1. Az
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    Az Hard slammed!

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    [Mar 9, 2012]
    Hi guys,

    I'm after some confirmation of what could be the problem on my s3 from anyone who may of experienced the same symptoms as what I am......

    The car was fine up until yesterday afternoon, it had a long motorway run for a good couple of hours with no problems, stopped at a service station for 10 minutes or so then the car wouldn't start and run. It would start up but then struggle to idle and then eventually stool. If I gave it some gas on start up it would fire up and then start to splutter and almost misfire with the revs not increasing past 1200 rpm or so (even though I had my foot down on the accelerator) sometimes it would increase in revs but it wasn't happy about it and stuttered throughout the rev range. If I reached underneath the car and gave the fuel tank a good couple of whacks then it started up, idled, and revved perfectly fine. BUT, since this has all happened it now hesitating in spots throughout the rev range when on 3/4's to full throttle, light throttle seems to be fine throughout the revs but I'm not sure if a hesitating would be that noticeable on such light throttle.

    Another possibility that crossed my mind was the crank sensor or coil packs, but both of those items were replaced on the car last year, the fuel pump relay was also replaced last year but I do know that it wasn't for a genuine audi relay. Those items were replaced by the previous owner when it wasn't starting at all.

    The car is a pre-facelift s3 with pretty high mileage of 154k, its remapped to 260-270 bhp and is running a full milltek system from turbo back with decat and induction kit, but it's had these mods for years with no issues. If anyone has had the same symptoms and can help out I'd much appreciate it before I go spending hundreds on a new fuel pump etc.

    Also if it is the full pump does anyone know of any there are after Market uprated pumps available such as walbro etc? Also what are the costs of a new fuel pump and fuel pump relay or crank sensor?

    Thanks in advance,

    Az :)
    Last edited: Mar 9, 2012
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  3. Az
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    Az Hard slammed!

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    [Mar 9, 2012]
    Appologies for how that text has come out, I did break it up into paragraphs to make it easy to read but it's come out as one big paragraph instead annoyingly! Is it cos I'm on my iphone?

    EDIT- Fixed!
    Last edited: Mar 9, 2012
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  4. s3dave
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    s3dave TFSI Hybrid

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    [Mar 9, 2012]
    Ive just changed mine, mine struggled to start first thing in a morning if the tank was under a quarter...it eventually just stopped working one morning...
    #3
  5. Reload
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    Reload Bird is the Word!

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    [Mar 9, 2012]
    Not sure about all of your symptoms mate, but a spluttering and sluggish revving could indicate one or more of your ignition could are gone
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  6. Az
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    Az Hard slammed!

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    [Mar 9, 2012]
    Did you have the same symptoms when driving yours at full throttle or under load? Now that you've replaced the pump is it all ok? I take it that it was just the pump you replaced and not the relay as well then?
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  7. Az
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    Az Hard slammed!

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    [Mar 9, 2012]
    Does anyone know if thr fuel pump relay has a use when the car is running? Or does it literally just send a signal to the pump on ignition to start the car up and that's it?
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  8. s3dave
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    s3dave TFSI Hybrid

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    [Mar 9, 2012]
    non of your symptoms it was fine once started i did not replace the relay,
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  9. Az
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    Az Hard slammed!

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    [Mar 9, 2012]
    Oh right, that's weird, if I had just the symptoms you had I would of put it down to the relay straight away if it was only on start up. I'm taking a wild guess mine is the pump as it just seems a bit weird that the start and idle seems to be fine if you give the fuel tank a whack, it seems to bring it back to life, but then I'm nit sure if that explains the flat / hesitation spots on full throttle......
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  10. s3dave
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    s3dave TFSI Hybrid

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    [Mar 9, 2012]
    Well if you are whacking the fuel pump and it sorts it...your telling yourself the answer....:)
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  11. Az
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    Az Hard slammed!

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    [Mar 9, 2012]
    I guess, do you think that would explain the hesitating under load as well then? Just looked at the RAC report as they came out to it (the guy was pretty useless before anyone asks and couldn't give a definate answer himself) but he's written on it 'poss fuel relay / pump fault, intermittent feed!' see that makes me wonder if it's more the relay if the pump has intermittent feed like he's stated?
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  12. Az
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    Az Hard slammed!

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    [Mar 9, 2012]
    Anyone else with any experience of this?
    Last edited: Mar 9, 2012
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  13. Az
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    Az Hard slammed!

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    [Mar 11, 2012]
    Quick update on this, car wouldn't start at work last night, the fuel gauge was showing 1/4 tank but when I had my mate bounce the car from inside the boot as I was laying on the floor next to it I could hardly hear any fuel swishing around in the tank. I did find a thread on here that a few people that own s3's and mk1 tt's have experienced running out of fuel when the gauge was still showing 1/4, so I'm now thinking that this could be my problem. The same thread explained how the pump has a suction jet that pulls fuel from the other side of the tank and if that's faulty then there could be 1/4 tank in one side of my tank which the gauge is showing, but no fuel in the other side of the tank where the pump is. So I'll be going back to work today with a jerry can of fuel to put in it to see if it starts and gets me to a petrol station to fill right up. I'll report back.......
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  14. A3 Oly
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    A3 Oly Member

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    [Mar 11, 2012]
    god damn i had this happen when someone was looking to by my t5 thought there was a decent amount of fuel in her but turned iut it was empty with a faulty dial
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  15. Az
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    Az Hard slammed!

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    [Mar 12, 2012]
    Had the AA come out to me yesterday and he confirmed that it is my fuel pump that is shot as it wasn't pulling any amps when the ignition was on, he tapped the white box on top of the fuel pump and it fired up straight away. So I will be ordering a new pump from audi today, not cheap though at £285 Inc vat!
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