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What causes the contacts on my cap and rotor to burn?

uid 7084's pic
posted by  Derek on  Wed Mar 27 04:19 CST 2002
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I checked my distributor cap and rotor last week and found the contacts burned (unknown mileage on them as I just bought the car). I installed new parts, cleaned and gapped the plugs, and checked the wires for continuity. 200 miles later the new cap and rotor are showing signs of burned contacts. What the hell is going on here? The car runs fine, in my opinion. The only complaint is lousy mileage which I am starting to blame exclusively on the 4.10 rear after much troubleshooting.
--
'89 745 GLE/5.0L/AOD (T-5 swap pending)








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    What causes the contacts on my cap and rotor to burn?

    uid 6548's pic
    posted by  Volvord 784VC on  Thu Mar 28 15:53 CST 2002
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    last visit: Wed Jun 20 02:46 CST 2007
    [RELATED]

    Hi Derek

    There will be arching between the rotor and distributor cap, what can accelerate the appearance of burning is higher resistance in the plug wires, worn plugs, plug gap too large, cheaper caps can have a larger rotor to cap gap, aluminum is not the best and brass is prefered. These just name a few, if the car is running good and without me seeing the cap/rotor I would say that what you are seeing is normal.

    Volvord 784VC
    Calgary, Alberta
    http://www.telusplanet.net/public/gilesij/Volvord/








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    What causes the contacts on my cap and rotor to burn?

    posted by  Dragwagon on  Wed Mar 27 12:07 CST 2002
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    last visit: Thu Dec 1 16:21 CST 2011
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    First, I hope you're getting caps and rotors with brass contacts and not aluminum. I've burned my share of those in the past. I thought it was plug gap until you said you checked it. Is your coil supposed to have an external resistor? And if it is, is it there? They'll work for a while without it but usually burn themselves out. Just a random thought and it's probably not the answer. I guess the only question is HOW burnt are they? Obliterated or slightly less? Still sounds strange. Good luck and sorry my ramblings aren't any help...just thinking out loud (but quietly, i guess since it's only typewritten words...)
    Oh yeah...you could always upgrade to D.I.S.!!!








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      What causes the contacts on my cap and rotor to burn?

      uid 7084's pic
      posted by  Derek on  Mon Apr 1 03:34 CST 2002
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      Thanks guys. The cap and rotor are Echlin, brass contacts. I dressed the initial (slight) burning with emery cloth and applied dielectric grease to the contacts. Seems to have settled down now (no additional deterioration). In any event, it wasn't weight-loss burning but rather just slight carbon deposit. Plug gap is (around) .050", plug wires are good. I'll check the resistor install - good tip.

      Cheers,

      Derek
      --
      '89 745 GLE/5.0L/AOD (T-5 swap pending)







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