Cracked Plug on a Scope

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  • Crusty
    Senior Member
    • Dec 2007
    • 2450

    #16
    Originally posted by crackerclicker
    The trace that shows "12" amps is just the scope picking up RFI/EMI from the bad plug. Sparking outside the cylinder tends to encourage interference on those big antennas we call current probes.
    This was Bob's comment in the first post. "I put a screen shot in here too of a normal coil firing with current ramp,"
    That wasn't the bad plug in the picture where the first CURRENT RAMP was.

    The second picture of a current ramp was the bad plug. The amplitude wasn't as high on the bad plug.

    The current changes with the bad plug. That's all I was pointing out.
    Without the "graph" selected on the scope screen and looking at the amperage on the left pink numbers, it isn't obvious.
    If Bob could pull up the movies and put "graph" display on, then drag the cursor across to where the current peaks, then it would show in the "min" "max" numbers at the bottom.

    Rich put up a pretty good description of the "multi-strike" system.

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    • crackerclicker
      Senior Member
      • May 2008
      • 400

      #17
      You're right about the pictures, but what I said about RFI still stands. Just so you know, I'm not picking a fight.

      Comment

      • Witsend
        Banned
        • Nov 2012
        • 2942

        #18
        01 5.4L F150 multi strike spark

        Yesterday evening I was in doubt and decided to whip it out scope (meaning drag out counselor 2) and scope a 2001 F-150 smoking from tailpipe and (P0304)with my counselor 2 with my COP set up , set the 2 sticks along the sides of coils with Side A facing coils with gain set to 6.5 and saw that this vehicle also has the multi-strike ignition style that Bob had on a 2005 , so these go away back before 2005
        I Noted lower KV on some cylinders but chalked it up to the stick on one bank ,not being close enough.
        I did a cranking amp test that didn't see a compression deficit on cylinder 4 , so I changed the plug and boot and advised customer the valve cover gaskets are leaking oil that is getting into the spark plug holes. The smoke from the tailpipe seems to persist however and #4 plug did not seem to have oil deposits showing on the electrodes. Coolant was low and I added but could not use my old Snap On Head gasket leak detector kit without an adapter for a degas bottle (kind of acrid smelling inside ) opening of degas bottle with cap off is larger than the typical radiator cap opening. Looks like I need to figure something out and fabricate an adapter cutting appropriate size hole with a hole saw through a salvage yard degas bottle cap .
        Attached Files

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        • Rich Shepherd
          Snap-on D&I
          • Nov 2006
          • 553

          #19
          Originally posted by Witsend
          Yesterday evening I was in doubt and decided to whip it out scope (meaning drag out counselor 2) and scope a 2001 F-150 smoking from tailpipe and (P0304)with my counselor 2 with my COP set up , set the 2 sticks along the sides of coils with Side A facing coils with gain set to 6.5 and saw that this vehicle also has the multi-strike ignition style that Bob had on a 2005 , so these go away back before 2005
          The multistrike systems on Ford go back quite a ways from 2001.
          I think it was around 91 that it was on an Escort.

          Comment

          • Witsend
            Banned
            • Nov 2012
            • 2942

            #20
            Uh Oh, Better get Geicco

            Well it looks like it's 3 strikes against me. Did the front end work , a rear axle shaft, rear speed sensor, and #4 plug and boot , and now this. El Crappo!
            Attached Files

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