1956 Johnson 30hp Only 1 Cylinder Firing

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  • July 10, 2024 at 11:36 pm #289051
    labrador-guy
    Participant

      US Member
      rhalbert10@outlook.com wrote:

      How do I do that?  Touch the sparkplug to the engine block while the engine is idling?

      If you have a test light you can pierce the spark plug hood with the pointed end of the test light while the motor is running.  That will kill that plug.  If that plug that you pierce make no difference in the way you motor is running you will know that plug is not doing it’s job.

      hope this helps.

      dale

      July 11, 2024 at 9:10 am #289054
      Buccaneer
      Participant

        US Member
        labrador-guy wrote:
        rhalbert10@outlook.com wrote:

        How do I do that?  Touch the sparkplug to the engine block while the engine is idling?

        If you have a test light you can pierce the spark plug hood with the pointed end of the test light while the motor is running.  That will kill that plug.  If that plug that you pierce make no difference in the way you motor is running you will know that plug is not doing it’s job.

        hope this helps.

        dale

        Just curious Dale, what does that operation do to the test light bulb?
        Don’t think I’ll try it on my new light.

        Prepare to be boarded!

        July 14, 2024 at 9:40 pm #289156
        dfs
        Participant

          Does this Johnson engine have a vacuum switch that grounds out one cylinder if RPMs runaway? Idle would be OK, but under load, vacuum switch setpoint or malfunction issue could shutdown a cylinder.

          July 27, 2024 at 7:12 pm #289475
          John Gragg
          Participant

            US Member

            Maybe I missed it? Have you done a compression test on each cylinder yet?

            Spark on both cylinders is great, but without compression you’re not going to get the pop you are looking for.

            Best Regards,

            John Gragg
            RIverside, CA

            Just starting in the hobby, please be patient.

            48 Sea King 5hp GG9014A
            49 Sea King 5hp GG9014A
            48 Johnson TD20
            49 Johnson TD20
            54 Johnson QD15
            55 Johnson CD12

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