Home Forum Ask A Member Testing coils, per1938 Bendix Scintilla procedure

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  • #283103
    Buccaneer
    Participant

      US Member - 1 Year (includes $3 online payment fee)

      I rigged up the Ford Model T buzz coil with a 6V game camera battery,
      and did the open air spark test per the shop manual.
      It fired the 3/16″ open air spark gap great before the video a few times.
      It did “okay” during the video, but afterward, only fired intermittent,
      or not at all, then NaDa.

      When I pushed the test button and it didn’t fire, I would hear a faint
      buzzing by the coils. Stupid me tried to see if I could feel which coil
      was buzzing / vibrating…… must have got too close to the secondary……
      Lit me up like a Christmas tree hooked up directly to the sub station
      transformer!…. OUCH!

      I turned the lights out in the garage, then pushed the test button again,
      and besides the buzz, I could see a faint glow, when looking under the
      rear coil.
      I pulled the magneto off again, separated the coils, and tested with
      the Stevens tester, using the “probe” function to look for leaks.
      I found none, and each coil fired on the Stevens at around 2 amps.

      Totally confounded now, but wondering if it’s a grounding issue between
      the magneto and powerhead mount, but that doesn’t make sense, as
      all the “grounding” was done atop the mag plate, not on the powerhead.

      The shop manual said to ground the Ford (T’s buzz ?) coil’s secondary,
      which I did to the mag plate along with the other grounds.
      Could that be an issue?

      The reason for the trouble shooting, when I originally finished
      going thru the magneto, new plug wires, condensers, etc.,
      One cylinder was sparking at the plugs better than the other,
      and it was determined not to be the spark plug.
      Also, I could not even get a “pop” out of the motor when using
      fogging oil, or gasoline in the carb, or cylinder.
      Compression is 65 psi on both cylinders, so I would think that’s
      good enough for a little action?

      https://youtu.be/Ofc3FbXO2bM

      Prepare to be boarded!

      #283105
      Tom
      Participant

        US Member - 1 Year (includes $3 online payment fee)

        Try grounding the T coil secondary to the bottom post on that coil.  I don’t think you want to be sending secondary voltage to the mag plate.

        Tom

        #283106
        Buccaneer
        Participant

          US Member - 1 Year (includes $3 online payment fee)

          Try grounding the T coil secondary to the bottom post on that coil.  I don’t think you want to be sending secondary voltage to the mag plate.

          Tom

          Tom, I may try going directly to the ground on the buzz coil tomorrow.
          I had all my ground connections at the mag plate, but the ground lead from the
          bottom of the coil was hooked up there as well.

          Prepare to be boarded!

          #283114
          The Boat House
          Participant



            You have found a leak. I have found that using
            the Merc O Tronic, to test the ignition this way
            has been the biggest benefit of having the device.
            Several times, after having a motor that wouldn’t
            start, I found a leak testing the coil this way.
            Tubs

            #283123
            Buccaneer
            Participant

              US Member - 1 Year (includes $3 online payment fee)



              You have found a leak. I have found that using
              the Merc O Tronic, to test the ignition this way
              has been the biggest benefit of having the device.
              Several times, after having a motor that wouldn’t
              start, I found a leak testing the coil this way.
              Tubs

              Tubs, I expected I had a “leak”, so I separated the coils again,
              and retested them on the Stevens, using the “Probe” to check
              for leaks…… no leaks found though.

              The “glow” and buzzing under the coils may have been from the
              secondary from the buzz coil being directly grounded to the mag
              plate, as Tom M. suggested. I haven’t had time to play today yet,
              but heading to the garage soon.

              Prepare to be boarded!

              #283133
              Buccaneer
              Participant

                US Member - 1 Year (includes $3 online payment fee)

                I redid the “grounds” on the magneto buzz coil test, this time with
                the magneto sitting on the bench. It jumped the 3/16″ gap with no
                troubles.
                I put it all back together and spun the motor over with a drill, and
                it will only jump less than an 1/8″ open air gap, and with the cordless
                drill on high speed.
                The grounding post that the arc jumps to, was grounded to the back
                side of the magneto, so it shouldn’t be a grounding issue from the magneto
                to powerhead.
                The magnets on the rotating magnet seem okay, but one half might
                possibly be a little stronger than the other.

                May re-check the point gap tomorrow, and maybe swap out the condenser,
                for lack of other ideas. Also, maybe I’ll run a permanent ground wire
                between the magneto to powerhead some how.

                DSCN8724

                VIDEO……..
                https://youtu.be/cnUkvjpXfBI

                 

                Prepare to be boarded!

                #283166
                jeff-register
                Participant

                  US Member - 2 Years

                  Tom,

                  To replace the vibrater coil a guy can use a double pole double throw relay. It vibrates to the normally closed contacts till they are pulled down & become open & spring open closing the other contacts causing an open/close action. Only one problem the pulsing action is too fast, added a .20mfg capacitor to slow down the charge rate to a mechanical rate & worked well. Fixed many merctronic viberators that way. Tried  with 555 chips timer chips & no good, they ran into thermo runaway & cook ed. Never tried silicone switching chips , SCRs.Even sounded like the mechanical vibrator.

                  Buck,

                  When using a dual fire coil, the spark plug with the lesser amount of resistance will fire to ground & the second hi volt terminal has enough electrical energy to fire the second output. Happens  in a split second. Try less resistance on your test pins by making the gaps a little differances. then you are putting the test close to actual running app’s.

                  #283177
                  Buccaneer
                  Participant

                    US Member - 1 Year (includes $3 online payment fee)

                    Tom,

                    To replace the vibrater coil a guy can use a double pole double throw relay. It vibrates to the normally closed contacts till they are pulled down & become open & spring open closing the other contacts causing an open/close action. Only one problem the pulsing action is too fast, added a .20mfg capacitor to slow down the charge rate to a mechanical rate & worked well. Fixed many merctronic viberators that way. Tried  with 555 chips timer chips & no good, they ran into thermo runaway & cook ed. Never tried silicone switching chips , SCRs.Even sounded like the mechanical vibrator.

                    Buck,

                    When using a dual fire coil, the spark plug with the lesser amount of resistance will fire to ground & the second hi volt terminal has enough electrical energy to fire the second output. Happens  in a split second. Try less resistance on your test pins by making the gaps a little differances. then you are putting the test close to actual running app’s.

                    Jeff, what you mention sounds similar to some plans I found years ago to rig up
                    battery ignition for a antique marine engine, using a Ford relay of some kind.
                    I can’t remember much about it, but it did work.

                    Currently the Bendix will only produce a weak
                    “open air gap” spark of less than 1/8″ inch when
                    spinning the motor over with my cordless drill on
                    high speed. I can’t even get the motor to fire on
                    fogging oil, or in desperation, ether!

                    Prepare to be boarded!

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