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Fuel Pump / Relay help

Discussion in 'A3/S3 Forum (8L Chassis)' started by Aaronneal, Feb 13, 2011.

  1. Aaronneal
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    Aaronneal New Member

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    [Feb 13, 2011]
    so my engine stuttered and cut out on me going round the M25 fri.

    So anyway narrowed it down to being the fuel pump and the relay.

    So after visiting GSF i got the relay and pump, however i was given relay 409 as a replacement.

    The problem is i cannot find 409 in my relay box or one that is a close equivalent.

    The Car is a 2000 A3 1.8t with an AGU engine. No matter where i look i cannot find much information on what relay i should have, although 409 is mentioned frequently as the fuel pump relay. But its not in my relay box.

    any help would b appreciated, i really need the car up and running tomorrow,

    Thanks

    Aaron
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  3. andymish
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    andymish New Member

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    [Feb 23, 2011]
    Hello there. My friend is also driving an A3 which he bought it as a second hand a couple months ago. Just last week, he also encounter a problem on his fuel pump relay and needs a replacement of it. He was also given a 409 as a replacement. Since he is still not quite familiar with his car, he also can't locate where to replace that 409 so we're both wondering if you were able to pinpoint it's location. Hoping you could update this post and share where it is.
    Last edited: Feb 23, 2011
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  4. karls s3
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    karls s3 Member

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    [Mar 10, 2011]
    im also trying to find fuel pump relay any one know where it is
    #3
  5. Imteyaz
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    Imteyaz 6th Gear

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    [Mar 10, 2011]
    Relay 409 is located behind the panel under the steering column / above where the pedals are - on the bottom row of relays, 4th relay from the left.

    (Bottom row should be: 1) Horn Relay No.53, 2) Ignition Relay No.100, 3:Blank / unknown, 4) Fuel Pump No.409)

    Hope that helps (and makes sense, it's too early in the morning for me to be even vaguely understandable normally!)
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  6. karls s3
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    karls s3 Member

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    [Mar 10, 2011]
    cheers mate thats great help. i spoke to audi this morning and found out my amk has two fuel pump relays one under bonnet by bulk head.
    #5
  7. Squirrelofdoom
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    Squirrelofdoom Member

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    [Jul 22, 2014]
    revisiting a long dead thread here...But, my car has recently struggled to start first time. Is taking two tries at least these days, sometimes 3. Could fuel relay be part of it?

    I haven't noticed any struggling when I get moving, it's just starting from cold that it struggles with
    #6
  8. SnowHammer
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    SnowHammer New Member

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    [Jul 28, 2014]
    I'm having the same issue with occasional not starting.. squirrel have you changed the fuel pump relay? any improvement?
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  9. RGL
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    RGL Free breather

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    [Jul 28, 2014]
    Any noticeable patterns in the not-starting?

    i.e.
    it doesn't start when it's cold?
    it doesn't start when the car has sat for a while?
    It doesn't want to start when the car is warm?

    or is it completely random?
    #8
  10. SnowHammer
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    SnowHammer New Member

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    [Jul 29, 2014]
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  11. Squirrelofdoom
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    Squirrelofdoom Member

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    [Jul 29, 2014]
    For me it's when the car is cold. Once it's going it's fine, and if it's been running and then I turn off for a few minutes, it'll start up again first try no problem
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  12. RGL
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    RGL Free breather

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    [Jul 29, 2014]
    You never know with the fuel relay, however it shouldn't necessarily affect only on cold starts, it should be more random if it is that.

    Sounds to me more like it's the fuel pump acting up and letting the fuel flow back into the tank once the car is stopped. In the pump there is sort of a valve there to stop it, however there are numerous cases of it failing. I think the only way to know for sure is to manually gauge the pressure in the fuel lines, to see how far and fast it drops once the engine has been shut off. The certain fix if it's the case is a new fuel pump. I've heard that some people tend to be stingier and just buy a new valve or whatever that goes into the fuel line. I've heard however that these sooner or later fail as well and overall seems to me like a crappy solution as I think it will probably disrupt atleast a little bit the normal flow of the fuel as well. However best to check it first to be sure, as the new pump isn't cheap.

    Other possible issue is the coolant temp sensor, however usually the water temp gauge in your dash goes bonkers once the temp sensor stops working properly as well and it shouldn't affect only the cold starts.

    Or there is a mix of different things. Always best to scan with VCDS/VAG-COM for any obvious clues first.
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  13. Squirrelofdoom
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    Squirrelofdoom Member

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    [Jul 29, 2014]
    well, I changed my fuel pump a couple of months ago, so that's brand new
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