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Thread: COP Testing

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  1. #1
    Scooting's Avatar
    Scooting is offline CHR Member Visit my Photo Gallery
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    Oct 2008
    Rio Rancho
    Car Year, Make, Model: 1940 Ford Sedan

    COP Testing


    On the late model 2 seater Thunderbirds, the coil on plug units have a large failure problem. Most are fixed by replacement and often good units are replaced to avoid future work. My question is how do you test a COP unit? What measurements can be taken and what are the range of good data numbers? On my Mark VIII Lincoln with the 280hp motor, can I look for the same numbers or do different coils have different values?
    I am looking for the true Mechanic's answer on testing rather than the drivers method of replacement or substution. Can you help?

  2. #2
    pepi's Avatar
    pepi is offline CHR Member/Contributor Visit my Photo Gallery
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    Dec 2006
    Car Year, Make, Model: 34,stroker,32pu,2020 MustangGTpp2

    The best suggestion I could offer is to compare the readings from a bad coil to a good coil. That will give you a reference or base line

    A coil is only a step up transformer, so either the windings are shorted or open. Numbers for resistance will be close, shorted will be the same, likewise an open will also read the same.
    I have two brains, one is lost and the other is out looking for it

  3. #3
    HWORRELL's Avatar
    HWORRELL is offline CHR Member Visit my Photo Gallery
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    Oct 2003
    Car Year, Make, Model: 31 FORD 5 WINDOW,69 442, 305 sprint car,

    Heres an article that gives Ford Cop checkout, completely useless procedure though unless you have the famous Ford breakout box.
    My Mitchell repair stuff has nothing on COP coil specs or testing.
    I would suspect since they have no specs its because no one wants to pay me my 99.50 per hour to test a coil X 8.. I know on Lincolns the book says if you have 1 bad one to replace all 8,thats a tuff sale. Heck if a Ford comes in with a miss fire all I need to know is which cylinder, pop the coil out,inspect the boot if its o.k. look at the plug and throw a new coil on it. Such a common problem it doesn't require a lot of testing.
    Coil On Plug Test

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