Why am I burning out Coils? | FerrariChat
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Why am I burning out Coils?

Discussion in '308/328' started by Big Daddy, Sep 14, 2012.

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  1. Big Daddy

    Big Daddy Karting

    Jan 3, 2009
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    Albuquerque, NM, USA
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    RJ
    #1 Big Daddy, Sep 14, 2012
    I have an '81 GTSi. Last year I noticed the front coil was cracked and sparking, so I replaced it with a new one of the same OEM type. The motor ran much better at low RPMs after that.

    Now it's running bad again, and it looks like the new coil is having the same problems.

    I want to know what is causing the problem. I've changed out the whole ignition system after the coils within the last year. Using a timing light I seem to be getting a spark on all four wires. I suppose it could be shorting to the block somewhere, but would that cause the coil to crack and short.

    I thought that since I have the electronic ignition I did not need a resistor on the coil. Am I wrong about that?
     
  2. BigTex

    BigTex Seven Time F1 World Champ
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    Dec 6, 2002
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    Bubba
    #2 BigTex, Sep 14, 2012
    I think the answer is "it depends"...but many replacement coils do need the ballast resistor.

    I use MSD epoxy potted units instead of the OEM oil filled, but keep the resistor.
    Still on stock distributor though.

    maybe some others will chime in.
    The MSD units are tough, and don't 'mind' being mounted horizontal.
     
  3. MNExotics

    MNExotics F1 Rookie
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    Ben Gruenzner
    #3 MNExotics, Sep 14, 2012
    If the coil you replaced the old one with is an old NOS the plastic maybe brittle and prone to cracking. I don't believe the i cars use ballast resistors.
     
  4. MNExotics

    MNExotics F1 Rookie
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    #4 MNExotics, Sep 14, 2012
    Last edited by a moderator: Sep 7, 2017
  5. alhbln

    alhbln Formula 3
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    Mar 4, 2008
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    Adrian
    #5 alhbln, Sep 15, 2012
    you don't need a resistor with a electronic ignition, the ignition will manage the coil current.

    defects in the secondary coil wiring and overheating of the coil usually indicate a too large gap in the distributor between the rotor and terminals or a problem with the phasing of the rotor (position of the rotor tip at the time of the spark discharge). the larger distance requires a higher voltage for the spark to discharge (jump the distance), which can overheat and damage the coil.
     
  6. plankeracer

    plankeracer Rookie

    Jul 6, 2011
    42
    Bergen Norway
    #6 plankeracer, Sep 15, 2012
    yes, also old sparkplugs or wrong gap on the plugs can cause heat that will burn the coil.
     
  7. rcraig

    rcraig F1 Rookie

    Dec 7, 2005
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    Bob Craig
    #7 rcraig, Sep 15, 2012
    Had my 79 308GTB converted to MSD/Petronix. Went through 2 coils within a month. Great friend/Mechanical Engineer/Lotus Mechanic helped me repair and insisted we switch to epoxy from oil.
    Not a single problem since.

    Bob
     
  8. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Steve Magnusson
    #8 Steve Magnusson, Sep 15, 2012
    After replacing the coil, one thing you might try is swapping the two DigiPlex ECUs (they are identical). If the rear coil then fails (instead of the front) that would be a sign that something inside the DigiPlex ECU (that is firing the failing coil) is the trouble. If the front coil fails yet again, then you know it is something downstream of the DigiPlex -- just a thought...
     

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