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Thread: M12 Won't Start

  1. #1
    Join Date
    Apr 2016
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    Cocoa, Florida
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    Default M12 Won't Start

    Looking for feedback.
    Drove my M12 two weekends ago, all was fine. Last weekend went to start it up and it would not start. It did sputter and backfire, but nothing. So today I've decided to do some trouble shooting....how hard could it be?
    So this is what I have.
    The fuel pump primes, and builds roughly 50 psi. When I crank the engine, the fuel pump does not come on, and pressure drops to zero. Additionally I am not getting any spark to the plugs. Tach needle never moves.
    I've checked the Crank and Cam sensors. (Even swapped them with new ones) I've checked all the fuses. (Even removed the 4 engine bay fuses and cleaned the contacts.) Removed and moved around locations of the 5 relays in the engine bay. (swapped the two grey ones with each other, and then also the 3 black ones)
    Still nothing.
    I also checked all the fuses in the passenger compartment. There are two relays side by side, one yellow and one red. What are these? The yellow one was warm and even with the key removed remains powered up.(which explains the current draw I've had ever since I've had this car.) If I pull a 10 amp fuse it turns off. (The fuse is the 10amp second from the left of the four horizontal fuses, not one of the 12 vertical ones)
    Thoughts??

    Thanks
    Eric

  2. #2
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    Apr 2016
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    Cocoa, Florida
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    Default

    Yellow relay is dome light delay relay.........

  3. #3
    Join Date
    Oct 2006
    Location
    Tallahassee
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    Default

    Quote Originally Posted by Ecmeric View Post
    Looking for feedback.
    Drove my M12 two weekends ago, all was fine. Last weekend went to start it up and it would not start. It did sputter and backfire, but nothing. So today I've decided to do some trouble shooting....how hard could it be?
    So this is what I have.
    The fuel pump primes, and builds roughly 50 psi. When I crank the engine, the fuel pump does not come on, and pressure drops to zero. Additionally I am not getting any spark to the plugs. Tach needle never moves.
    I've checked the Crank and Cam sensors. (Even swapped them with new ones) I've checked all the fuses. (Even removed the 4 engine bay fuses and cleaned the contacts.) Removed and moved around locations of the 5 relays in the engine bay. (swapped the two grey ones with each other, and then also the 3 black ones)
    Still nothing.
    I also checked all the fuses in the passenger compartment. There are two relays side by side, one yellow and one red. What are these? The yellow one was warm and even with the key removed remains powered up.(which explains the current draw I've had ever since I've had this car.) If I pull a 10 amp fuse it turns off. (The fuse is the 10amp second from the left of the four horizontal fuses, not one of the 12 vertical ones)
    Thoughts??

    Thanks
    Eric
    Call me and lets chat about the diagnosis
    -Troy Fralick
    troy@nobleupgrades.com
    Tallahassee Speed Shop, Inc.
    5338 Gateway Drive
    Tallahassee, Fl 32303
    850-597-8919
    904-838-9150 cell
    And
    Remade by Hand, Inc.
    Porsche Restorations
    173 McCallister Rd
    Crawfordville, FL 32327

  4. #4
    Join Date
    Apr 2016
    Location
    Cocoa, Florida
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    Default

    Easymap 5 sees and talks to ECU, even controls stuff using test function. But no RPM when cranking.
    Comparing the Cam sensor to the crank sensor.....The cam sensor has a ground and 5VDC. Crank sensor has ground but no voltage. When key is off, the power lead on the cam sensor shows resistance, the crank sensor shows "open".
    Checked continuity from crank sensor to ECU plug (A1 on brown plug) and I have continuity. So wire is not broken between the sensor and the ECU.
    Whats left? Broken wire inside ECU? Am I missing something?

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