Carbon button in Marelli distributor? Help. | FerrariChat
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Carbon button in Marelli distributor? Help.

Discussion in '308/328' started by climb, Jul 17, 2022.

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  1. climb

    climb F1 Rookie

    Sep 19, 2006
    4,866
    Atlantic Beach Fl
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    Stuart K. Hicks
    #1 climb, Jul 17, 2022
    So I’ve been chasing a rough running hart start condition on my ‘80 ‘i’ NA spec and took off the distributor caps looking for answers. Found one of the carbon buttons had turned chalky and seems the spring is not keeping it well, sprung. What is the purpose of the button and how do you get the spring in the hole when it’s diameter is wider than the hole? Could this be part of my problem? Here is a pic. Thank you.
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  2. climb

    climb F1 Rookie

    Sep 19, 2006
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    Stuart K. Hicks
    #2 climb, Jul 17, 2022
    Hard start and difficult to get to rev.
     
  3. climb

    climb F1 Rookie

    Sep 19, 2006
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    #3 climb, Jul 17, 2022
    For comparison here is the other distributor’s carbon button. Spring loaded and not chalky.
    View attachment 2492037
     
  4. climb

    climb F1 Rookie

    Sep 19, 2006
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    #4 climb, Jul 17, 2022

    Attached Files:

  5. climb

    climb F1 Rookie

    Sep 19, 2006
    4,866
    Atlantic Beach Fl
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    Stuart K. Hicks
    #5 climb, Jul 17, 2022
    Didn’t mean to post this pic. Can’t see a delete function so please disregard.
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    26,794
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #6 Steve Magnusson, Jul 17, 2022
    Last edited: Jul 17, 2022
    By "winding" the spring in the direction of the coils (i.e., sort of wedge the back end of the spring into the hole and then twist the spring in the direction of the coils to reduce its diameter while pushing it, and the button, in).

    Yes. You need the spring-loaded carbon button to be in contact with the metal surface of the rotor. Any "gap" there is another gap that the spark needs to jump. Your "bad" button looks broken where the spring attaches. Pull out both and compare them.

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  7. climb

    climb F1 Rookie

    Sep 19, 2006
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    #7 climb, Jul 17, 2022
    Thank you!
     
  8. Patrick Dixon

    Patrick Dixon Formula 3

    Mar 27, 2012
    1,130
    UK
    #8 Patrick Dixon, Jul 18, 2022
    The carbon button is part of the HT circuit from the coil to the individual spark plugs. It connects the coil lead to the top of the rotor arm which then connects to each spark plug lead in turn as the rotor rotates in the distributor cap. So it's pretty important that it makes good contact!
     
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  9. climb

    climb F1 Rookie

    Sep 19, 2006
    4,866
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    Stuart K. Hicks
    #9 climb, Jul 18, 2022
    I always put it in but never mind even realized that until now. I thought maybe it was something that absorbs wayward sparks or I dunno ‍♂️ what. Makes sense now that I think about it. Sends current from coil into rotor arm, rotor connects to each contact as it spins etc. Going to order new ones. Hope I can get the damn spring in right this time. Know it’s easy if you’ve done it but I had a helluva time getting it in last time and this problem was end result. Luckily they’re cheap I guess. :)
     
  10. Brian Harper

    Brian Harper F1 Rookie
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    Feb 17, 2006
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    #10 Brian Harper, Jul 19, 2022
    Just for clarity it doesn't connect, it gets really close and the spark jumps the gap. But yes, you have the idea exactly right.
     
  11. climb

    climb F1 Rookie

    Sep 19, 2006
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    Stuart K. Hicks
    #11 climb, Jul 19, 2022
    I see. Thanks
     

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