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Vacuum in fuel tank

Discussion in 'A4/S4 forum(B5 Chassis)' started by russ g, Nov 13, 2009.

  1. russ g
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    russ g New Member

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    hi there i have had an audi a4 1.8t for a couple of months now and having a bit of trouble with it. When we filled the fuel tank for the first time most of it ended up on the forcourt, when i looked at it found the fuel sender seal had been sucked in. So the leak was coming from there so refitted seal and all was good for a little while till car stopped, got out and took the fuel cap off big release of pressure so tried car with fuel cap removed and car ran fine. ive heard that the evap n80 valve could cause the vacuum in tank is there any way of testing this? if so i would be very greatful if someone could tell me how to do this.

    cheers russ
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  2. s4 v tm
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    s4 v tm New Member

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    change the fuel cap most have a one way valve in them that consists of a spring and ball bearing that allow air in to the tank as the fuel level drops. had this problem before
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  3. gruf
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    gruf Member

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    my car lets a load of air out when i fill up, is this a bad thing,
    the car seems ok and dont ever have any running trouble.
    should i change my cap
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  4. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator

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    Sounds like a broken N80 valve.

    I dont think the fuel caps are vented on these, it just uses the N80 to vent the tank.

    If the valves broken you'll probably have a fault code logged.

    Its also likely the vacuum caused by the broken valve is what killed the tank seal in the first place.
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  5. russ g
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    russ g New Member

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    hi there just like to say thanks to your reply i had checked for codes when i first got the car and im pretty sure the n80 was listed as a fault code but i cant find the bit of paper i had written them on. i did try removing the n80 with the car running it was still plugged in but the two pipes removed it was marking like a clicking sound then after a while (couple of mins) it stopped then would cut in again is this normal? is there anyway of testing this n80 valve any help would be very greatfull

    thanks russ
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