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Thread: Need diagnosis help

  1. #1
    Registered User SAF's Avatar
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    Need diagnosis help

    Hey all. My almost dearly departed beast has a new problem that the shop can't seem to figure out.

    It doesn't start. Sometimes. Four times actually. It turns and turns but won't fire up. Then (at least those 4 times) after a few minutes it would go like nothing was wrong. The last time I gave up before wearing battery down, went back hours later and it started, so I took it to my shop. Seems like it would always start in the morning but it would fail to catch when I jump in after parking somewhere. Occasionally.

    They said no codes pointed to anything. They are putting in a few hours testing wiring at this point, but I'm not going to let that go on forever on the clock. Any ideas?
    Thanks for any input, I'll check in later.

  2. #2
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    Theory #1:
    Open ECU, check if it had a chip soldered in previously.
    Any obvious soldering, that doesn't look factory.

    Also, if its' ECU - when it doesn't want to start, your MIL won't light up on ignition on. Or your tach needle won't move when you're cranking.

    Theory #2:
    G28, crank position sensor. It would likely have thrown a DTC, though.

  3. #3
    Registered User mrdave's Avatar
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    Clogged fuel filter/line? Bad fuel pump relay? Bad gas?

  4. #4
    Registered User ttboost's Avatar
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    Does fuel pump prime?
    2013 Audi S8

  5. #5
    Registered User SAF's Avatar
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    confirming fuel flow this morning. After that I told them to quit the open ended search.

  6. #6
    Registered User SAF's Avatar
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    Well shit, nothing found wrong with fuel flow. I can't believe they couldn't narrow this down.
    Going to bring it home tomorrow from the shop. Then I'm not sure what I'm going to do. Definitely don't have money to throw at random electronics testing and frayed wire search in hopes it fails at the right time.

    Might be time to bail.

  7. #7
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    Quote Originally Posted by nubcake View Post
    Also, if its' ECU - when it doesn't want to start, your MIL won't light up on ignition on. Or your tach needle won't move when you're cranking.
    Seriously, pay attention to this.
    It will give you enough info.

  8. #8
    Registered User SAF's Avatar
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    Quote Originally Posted by nubcake View Post
    Seriously, pay attention to this.
    It will give you enough info.
    Yeah none of that is happening. Never had a chip put in it.
    She started up today at the shop and I shot home and parked it in my driveway... Bumming.

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