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  1. #1
    Active Member One Ring
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    Dec 28 2014
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    St Louis, MO

    Source of vacuum for reservoir

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    TL;DR: when the N249 is bypassed, what is the source of vacuum for the vacuum reservoir inside the front fender? The line that used to connect the N249 and the reservoir has been capped.

    Hey! I'm getting an error code for my leak detection pump (LDP). I don't remember the code from the vagcom at the moment, I've been debugging for a long time. But it fails test 071 on the vag com.

    2000 B5 S4, manual (in case it matters)

    Steps I've performed so far include:

    1. smoke test the lines from the N80 all the way to the LDP in the rear fender
    2. the N80 tests fine (070 ok)
    3. replace the LDP with a brand new one
    4. replaced the seal on the gas cap, then replaced the whole gas cap to be sure

    When I run the tests on the LDP it shows that the "REED" never opens. This lead me to wondering if there was no vacuum available to open the reed inside the LDP.

    From there I checked the lines between the LDP and the vacuum reservoir and couldn't find any obvious leaks (though I'll probably try to smoke test it soon).

    The line that used to connect the N249 (bypassed when installed 034 fuel rails because they say it's okay to do so) and the reservoir has been capped. Seems like if that is the only source of vacuum to the reservoir it needs to be reconnected to the intake manifold somehow.

    Thanks for your help/opinions/advice!

  2. #2
    Senior Member Three Rings LJS's Avatar
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    Apr 08 2013
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    112983
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    15 VW GTI S-Very WHITE
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    Connecticut

    This may help--
    Here's the OE vac routing---Hose-22 is on base of intake (near the brake booster vac hose), Hose-17 feeds the vac reservoir.
    You simply need to add a hose from the base of the intake-where Hose -22 was-add a check valve and attach to the where Hose -17 was(hard line).[IMG][/IMG]
    QUESTION- Why would you eliminate the N249 circuit???
    PS- the N80 valve(other side of the motor) controls the vac signal to the LDP.

  3. #3
    Active Member One Ring
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    Quote Originally Posted by LJS View Post
    QUESTION- Why would you eliminate the N249 circuit???
    PS- the N80 valve(other side of the motor) controls the vac signal to the LDP.
    ANSWER - I was young and naive and the 034 directions for the fuel rail said N249 was unnecessary but did NOT include instructions for how to remove/bypass. I didn't get an error code until recently (years later) *somehow *shrugs*.

  4. #4
    Active Member One Ring
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    Is this (line 17) the only source of vacuum for the reservoir?

  5. #5
    Active Member One Ring
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    Jan 10 2017
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    French Creek

    Any vac source on the mani will prob do, but dont forget a check valve to keep to keep boost out of it.
    I might shoot for the brake booster if you are deleting stuff.
    Obviously stay away from the fuel pressure reg line. dont want any funk going on when its turning on and off.

    Last 034 rail on I just reconfigured the n249 and n80 check valve stuff and hid it under the mani.

  6. #6
    Active Member One Ring
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    Dec 28 2014
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    St Louis, MO

    I appreciate all the answers! I'm not looking for a new source, I'm trying to identify what would normally be the source.

    I guess I'm not asking the right question. To put it another way: I'm wondering if there is another thing already adding vacuum to the reservoir (like, does it have its own pump?) and that maybe this unknown part has failed.

    Trying to reason about how this was working for some period of time despite the current configuration, with the line that should be connected to the N249 vacuum line setup being disconnected and capped off.

  7. #7
    Active Member One Ring
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    Jan 10 2017
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    Where does hose 22 go on the mani? Use that (with some sort of check valve).
    The 01.5+ is kinda similar, but comes off the top of the mani.

    ETA Just looked at one. If you are getting rid of the n249, use that one on the back of the mani.

  8. #8
    Active Member One Ring
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    Quote Originally Posted by neilthewheel View Post
    Where does hose 22 go on the mani? Use that (with some sort of check valve).
    The 01.5+ is kinda similar, but comes off the top of the mani.

    ETA Just looked at one. If you are getting rid of the n249, use that one on the back of the mani.
    The N249 has already been removed. I'm trying to identify if the vacuum reservoir might be hooked up to some _other_ source already. I'm not trying to decide where I should hook it up, I've already got info on this thanks to you and LJS.

  9. #9
    Active Member One Ring
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    Jan 10 2017
    AZ Member #
    390358
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    French Creek

    If its not a open or short code on the ldp, then you dont have vac going to it.

    That code almost bit me once. Only code the car had, and crank/no start.
    The coils are on the same fuse as the ldp so if wiring goes bad under the boot, it takes out the fuse, and that code can send you on the goose chase



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