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Ignition problems

Discussion in 'Technical Q&A' started by sunburn, Dec 9, 2003.

  1. sunburn

    sunburn Formula Junior

    Nov 2, 2003
    693
    Dawsonville, GA
    Full Name:
    Rick R.
    I just bought a 1995 456 GT and need some assistence in how the ECU triggers the coil packs. The car has developed a missfire (actually no spark at all on cylinders 2 and 5). It was happening when it was cold and then it would go away. Today it continued even once the car was warm. There is no spark for those cylinders directly from the coil pack so I've eliminated any plug wire issues. The system never shows a check engine light but will show a slow down 1-6 light if the car is run for 5 miles or so at 35-45 mph.

    First, does the car have an ECU for each bank of cylinders? I can only find 1 under the drivers side kick panel.

    Second, does the ECU drive the 12V trigger to the coil pack or are there separate ignition amps.

    Third, has anyone heard of a coil pack failure that only effected 2 cylinders?

    Thanks for any insight you can give.
     
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  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    21,044
    Texas
    Full Name:
    Steve Magnusson
    Have you read your OM carefully? -- IME often there are good architechtural descriptions given (e.g., 1 or 2 ecu for a particular function).

    Agree that it's a strange problem, but if you've truly got 2 non-firing cylinders in a bank then the warning light is probably doing it's job well and shouldn't be ignored.

    Give us non-456ers a description regarding "coil packs" -- are you distributorless? -- does each bank have its own (swappable?) pack?
     
  4. james patterson

    james patterson Formula Junior
    Professional Ferrari Technician

    Dec 8, 2003
    417
    Dallas Texas
    Full Name:
    James Patterson
    Your problem is most likely the coil pack, it is a wasted spark system with 2/5 sharing the same coil, 3 coil per pack. We have had a number of this style coilpacks fail on 348,512 models. As Mr. Magnusson suggested ,to make sure, swap the coils from bank to bank and see if the problem does not move to the 7/12. Good luck.
     
  5. sunburn

    sunburn Formula Junior

    Nov 2, 2003
    693
    Dawsonville, GA
    Full Name:
    Rick R.
    Thanks for the input guys. The 456 is without distributor. It does have 2 coil packs, one for each bank so a swap is the next step. The task is not an easy one as the bolts that hold the packs in place were most likely the first pieces to come down the assembly line and the car was built around them.
     
  6. sunburn

    sunburn Formula Junior

    Nov 2, 2003
    693
    Dawsonville, GA
    Full Name:
    Rick R.
    Good call James! I replaced the coil pack for the 1-6 bank and we're back in business . . . and the great thing is it was under $200 bucks. It seems like I can't even change the air in the tires for under $200 bucks!
    Thanks for the input.
     
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  8. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,375
    USA
    Wow! That is awesome.
     
  9. DGS

    DGS Four Time F1 World Champ
    Rossa Subscribed

    May 27, 2003
    44,035
    MidTN
    Full Name:
    DGS
    No, no, no. The japanese build cars that way.

    On italian cars, you maneuver the bolt (more likely nut) into place by hand (relying on thin dextrous fingers (which make you popular with le ragazze)).

    Then you wrap a strand of al Dente Linguini around the part with the long end routed through the labyrinth to where you can grasp it.

    Go have some wine.

    When you return, the hardened pasta becomes your custom wrench.

    When the pasta shatters and breaks away from the part, it's "tight enough".

    That's why it's so hard to find torque settings for these cars in newton-metres. They're calibrated in percent-litres. (Litres of wine consumed at a given percent relative humidity before tightening.)

    :D
     
  10. Fennicus

    Fennicus Formula Junior

    Apr 10, 2015
    573
    Helsinki, Finland
    Full Name:
    Pekka T.
    Hi all,

    This is a very old thread, I know, but as I could find almost nothing on the coil packs on 1992-1996 456GT’s and their spark plug wiring in the WSM or here, I thought I should post.

    My dilemma: the engine works well, no issues, except very rarely when the engine is not yet warm and I pull up a ramp and the revs drop it may light a CEL which always goes away.

    BUT as I was taking out the spark plug wires as part of a service I noticed some weird things with the wiring.

    Some previous mechanic has marked the coil pack and the ends of the wires with corresponding white dots. Good. On the RH side they match the spark plug wires, but on the LH side they do not.

    Are they connected wrong?

    Looking from the front.
    The RH side, spark plugs 1-6:

    3 2. 1
    4. 5. 6

    Also on that side there is a white dot, like on a dice, that matches the wires, on both the coil pack and the spark plug wire boot.

    •••. ••. •

    ••. •••. •••
    •• . •• •••

    BUT on the LH side for spark plugs 7-12 they are now connected like this:

    11.12.10
    8. 7. 9


    And the coil pack is marked:

    •••. ••. •

    ••. •••. •••
    ••. ••. •••

    But the spark plug wire boot markings don’t match, they are like this:

    ••. •. •••

    ••. ••• •••
    ••. •• •••

    So the LH side 7-12 was wrong when some previous mechanic made the white markings and my two latest services in Germany fixed that and connected the wires right?

    Or some if those spark plug wires are now incorrectly connected but the engine runs fine?

    I know this is a “waste spark” system, so if a plug is close to being 180 deg off it will fire correctly, and in a 12 cyl engine very small misfiring is hardly noticeable?

    if anyone knows where I can check how the coil packs shoud fire, I would appreciate the info.

    This is of course the early firing order: 1-12-5-8-3-10-6-7-2-11-4-9

    So right bank is the classic 1-5-3-6-2-4 and left bank in the same order from the front 12-8-10-7-11-9.

    Cheers!
     
  11. Qavion

    Qavion F1 Veteran
    Silver Subscribed

    Feb 20, 2015
    5,884
    Sydney
    Full Name:
    Ian Riddell
    For what it's worth, I've been told that the early 456's are the same as the 550.

    The 550 coil pack outlets pairs appear to be numbered 1~3, with output pair 1 closest to the 4 pin plug.

    Image Unavailable, Please Login

    I've also been told the the left bank (7~12) coilpack has an outlet pair firing order 2-1-3. For the right bank, the coil pack firing order is 3-2-1.

    The paired spark plugs are (order yet unknown) 1-6, 2-5, 3-4, 7-12, 8-11, 9-10. If you know the 12 cylinder firing order and the coilpack pair firing order, then perhaps you can figure out which leads are supposed to be connected to which coil pack pairs.


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    e.g. In firing sequence...
    Right bank coil pack outlet pair 3 should be connected 1 & 6.
    Left bank coil outlet pair 2 should be connected to 12 & 7.
    Right bank coilpack pair outlet 2 should be connected to 5 & 2
    Left bank coil outlet pair 1 should be connected to 8 & 11
    Right bank coil outlet pair 1 should be connected to 3 & 4
    Left bank coil outlet pair 3 should be connected to 10 & 9

    Is this what you were looking for?

    As always, I stand to be corrected.
     
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  13. Qavion

    Qavion F1 Veteran
    Silver Subscribed

    Feb 20, 2015
    5,884
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    Ian Riddell
    #10 Qavion, Feb 7, 2021
    Last edited: Feb 7, 2021
    Ugh.. disregard that cylinder diagram with the lines on it. Not sure where I got it from, but it disagrees with the 550 firing order.

    This is better

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    1 - 12 - 5 - 8 - 3 - 10 - 6 - 7 - 2 - 11 - 4 - 9
     
  14. Fennicus

    Fennicus Formula Junior

    Apr 10, 2015
    573
    Helsinki, Finland
    Full Name:
    Pekka T.
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    Hi,

    Yes! Thank you, now it all makes sense.

    And don’t worry about the firing order, the early ”classic Jano 60/65deg firing order” is what it is.

    The pairs are of course the cylinders which are 180 deg from each other timing wise 1-6, 2-5, 3-4 etc as the system fires twice for each crank rotation.

    So the wires are correctly fitted, and only the markings from the unknown past were wrong. (See pic)

    Cheers!
     
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