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Boost gauge only reads negative boost?

Discussion in 'A3/S3 Forum (8L Chassis)' started by garyrmills, Oct 11, 2009.

  1. garyrmills
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    garyrmills Member

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    [Oct 11, 2009]
    when i fitted my boost guage it worked fine for a week or so then it started to only read negative pressure.
    ive got the pipe t'd into the dump valve breather on the top of my oo7p its not a blocked pipe as ive changed the pipe for stronger pipe and its still doing the same? the boost wont read over 0 psi. ive also tryed a new guage and t peice any ideas would be great :think:
    thanks in advance gary
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  3. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Oct 11, 2009]
    try t'ing it correctly, you need to T into a inlet manifold vaccum line
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  4. djdougalno1
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    djdougalno1 Member

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    [Oct 11, 2009]
    i dont think it makes much difference any of the vacuum hoses will do have u got any leaks like around the t piece any split hoses
    #3
  5. garyrmills
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    garyrmills Member

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    [Oct 11, 2009]
    Any chance of pics as im not sure which pipe to go to either that or abit of an explanation please mate. Is strange that it worked on the hose from top of dv before and not after a while tho?
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  6. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Oct 11, 2009]
    it does make a difference as you need manifold pressure not just any old vaccum pressure, the line from the dump valve goes through the n249 valve so its never going to give correct readings.
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  7. s3_kev
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    s3_kev Stage2'd!!!!!!

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    [Oct 11, 2009]
    it does seem strange that it was ok and now its not, yeah it does work using the line from the dump valve but its not an accurate enough route, the line from the fuel pressure regulator is a good one thats the little valve on the right hand side of the fuel rail as you look at it
    #6
  8. garyrmills
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    garyrmills Member

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    [Oct 11, 2009]
    nice 1 il have a looky tommorow
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  9. S3 Nattie
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    S3 Nattie Quattro ist für sissies

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    [Oct 11, 2009]
    You could also T it into the fuel pressure regulator. Check that the piping that goes to the gauge has not folded or twisted on itself.
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