Ignition cutting out

Discussion in 'Electrical Systems' started by Jreid2010, Dec 1, 2017.

  1. Jreid2010

    Jreid2010 New Member

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    Jul 4, 2016
    Arkansas
    I'm not sure where to post this but decided to go electrical. Hoping someone might have experienced this same issue and can point me in the right direction. Any ideas, suggestions or help would be awesome, thanks in advance.

    400 small block recently rebuilt, 449 HP, quick fuel carb, headers, Ready to run MSD ignition set up broken in on the dyno and tuned, it idols at 900 RPM's. It has run perfect for about 6 months with no problems and now this issue. At idol, for no rhyme or reason the car will begin to "spark knock" or loose idol. It will drop from 900 RPM's to about 400 and struggle to run. If I give it gas it will come out of the issue and go back up to normal idol. This problem is not constant as it will only happen intermittently. It seems as though it's loosing power but none of the other components experience electric issues at the time.

    Things I've done. Tuned carb, checked power valve, adjusted curve on distributor, checked all wires for good connection, replaced spark plugs. I've checked the volts at the coil and when the problem is occurring I'm not getting a drop in voltage at the coil? I believe I have ruled out it being a carb issue?
     

    Attached Files:

  2. COPO

    COPO Veteran Member Lifetime Gold Member

    15,924
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    Sep 15, 1999
    Ontario, Canada
    How’s the float level, how old is the fuel filter and what’s your plug gap?
     
  3. Jreid2010

    Jreid2010 New Member

    13
    0
    Jul 4, 2016
    Arkansas
    Float level is good, that was looked at early on. Fuel filter is old as the motor and I don't know the gaps on the plugs.
     
  4. dave@ztech

    dave@ztech Veteran Member Lifetime Gold Member

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    Mar 27, 2016
    NY
    Does , it seem to happen , more after you have driven it for a while, or happen only when cold, does it happen several times in a row, or just once in a blue moon?
     
  5. Jreid2010

    Jreid2010 New Member

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    Jul 4, 2016
    Arkansas
    It’s hit and miss. Last night it happened right after I started it up. The other day I left it running for 1 hour and it never did it. Sometimes it will happen sitting at a stop light.
     
  6. dave@ztech

    dave@ztech Veteran Member Lifetime Gold Member

    368
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    Mar 27, 2016
    NY
    Did you check, very carefully the wires coming from the starter that come close to the headers, feel them with your hands and make sure you don't find any melted spots, and carefully look at all the wires that are even close to the headers, to make sure they are not arcing to the headers, also is there a difference on the days, for example, just after a rain? high humidity , after washing the car?
     
  7. COPO

    COPO Veteran Member Lifetime Gold Member

    15,924
    179
    Sep 15, 1999
    Ontario, Canada
    I had a dirty fuel filter a couple of yrs ago and it did not feed fuel properly and chugged a bit while driving.
    It felt like the car was going to die and forget about accelerating smoothly.
     
  8. dave@ztech

    dave@ztech Veteran Member Lifetime Gold Member

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    Mar 27, 2016
    NY
    Hi Mark,
    but a fuel filter would be constant problem, correct, not intermittent , like the problem the OP is asking about . Right?
     
  9. Jreid2010

    Jreid2010 New Member

    13
    0
    Jul 4, 2016
    Arkansas
    Dave,
    When the drop in RPMs is happening the engine is detonating. Im thinking along your lines as a wiring problem.
    Wonder if a bad coil could cause symptoms like this?
     
  10. COPO

    COPO Veteran Member Lifetime Gold Member

    15,924
    179
    Sep 15, 1999
    Ontario, Canada
    Fuel filter would be constant.
     

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