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Results 1 to 8 of 8
  1. #1

    Default 1982 70 hp Johnson ignition problem

    I have a 1982 Johnson 70 that when I first start it #1 cylinder does not fire, only runs on 2 & 3. Usually if I let it run after a while (10-15 minutes) #1 will start to fire, intermittenly at first then eventually it runs okay. But I have had times when #1 won't fire all day? I have already replaced the power pack, rebuilt the carbs (I realize that has nothing to do with spark) and installed new plugs. Any reason the motor would have to "warm up" before #1 cyclinder will fire?

  2. #2
    Join Date
    Nov 2005
    Location
    Chesapeake, Va, US
    Posts
    1,111

    Default Re: 1982 70 hp Johnson ignition problem

    Compression check??
    Bill H PTC USN Ret
    A manual is a cheap investment.

  3. #3
    Join Date
    Nov 2005
    Location
    Mt. Zion, Illinois,
    Posts
    185

    Default Re: 1982 70 hp Johnson ignition problem

    Quote Originally Posted by kybassn View Post
    I have a 1982 Johnson 70 that when I first start it #1 cylinder does not fire, only runs on 2 & 3. Usually if I let it run after a while (10-15 minutes) #1 will start to fire, intermittenly at first then eventually it runs okay. But I have had times when #1 won't fire all day? I have already replaced the power pack, rebuilt the carbs (I realize that has nothing to do with spark) and installed new plugs. Any reason the motor would have to "warm up" before #1 cyclinder will fire?
    Have you verified spark on all 3 cylinders using a spark tester? Each plug should have sufficient spark to jump a 7/16" gap. Something like this In-line adjustable spark tester would work great, or you can use a homemade unit. Search this forum for spark testers posted by Joe Reeves for instructions how to do this.

    Compression test is an absolute must.

    2-stroke engines need 3 things to run: Fuel, spark, compression. Verify good spark and compression on all three cylinders. If you've never rebuilt the carbs, that's a good idea. However, the fact that it runs sometimes and 10 or 15 minutes doesn't sound like a fuel delivery issue. If the problem is a plugged carb the engine won't run worth squat no matter how long you let it warm up.

    KJ

  4. #4

    Default Re: 1982 70 hp Johnson ignition problem

    #1 = 125 #2 = 120 #3 = 130. I had rebuilt the motor about 10 years ago and have used very little the past 8 years. The spark problem started about 5 years ago. I mostly ignored it because after a few minutes it would run fine. Then I had a couple of episodes when it never did fire on all 3 cylinders. Put the muffs on it today, ran on 2 & 3 for about 10 minutes then you could hear 1 starting to fire sporadically. After a few minutes it was hitting on all 3 and ran fine. If I thought that would be the case everytime I could live with it. But I don't want to get stuck out on the lake in the middle of the night.

  5. #5

    Default Re: 1982 70 hp Johnson ignition problem

    Have a spark tester. Good spark on 2 & 3, nothing on 1. Then after I let it run a while it starts firing on 1. I rebuilt the carbs yesterday and checked compression this morning. All good.

  6. #6
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    9,768

    Default Re: 1982 70 hp Johnson ignition problem

    do the resistance tests on the CHARGE COILS and also on the SENSOR COILS.------------Check all the pins / sockets in the plug in connecters.

  7. #7
    Join Date
    Apr 2006
    Location
    , Langkawi, Malaysia
    Posts
    5,750

    Default Re: 1982 70 hp Johnson ignition problem

    Verify that you have about 250 Volts (AC) into the coil, and if possible use a timing light to verify that you have ignition in the plug lead.
    Mark out the fly-wheel when 2 and 3 are on TDC as well.
    Crank the engine, check with the timing light that each cyl fires at correct position, and only then.
    When pick-up hooked to #1, only timing marks for #1 should be visible, no other marks. Move on to #2 etc.
    Use a spark-tester and verify with a 7/16 gap to verify the strength of the spark.
    If spark, remove the carb cover and spray some fuel (2%) into the carb throat and see if it fires.
    If that helps, you have a fuel supply/carb problem.

  8. #8

    Default Re: 1982 70 hp Johnson ignition problem

    Okay, borrowed a cheap meter and tested the ignition coils. All 3 coils were good on the primary winding test, but #2 coil failed secondary winding test (should be 275 +/- 50 ohms and it was 0. Confused because my issue is with #1 not firing I performed a spark gap test. 2 & 3 had strong spark at 7/16" gap, #1 no spark???? Looked over the pins and wire connections and best I can tell all is fine. Power pack is brand new, I replaced it because of the problem with #1 not firing. Tempted to buy a new set of coils, even though I cannot understand how a bad secondary winding test on #2 could have anything to do with no spark on #1???

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