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1989 Yamaha 20 HP missfire

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  • 1989 Yamaha 20 HP missfire

    I have a 1988 Yamaha 2 stroke 20 Hp that is misfiring. I got this engine from a lady who told me her grandfather bought it new, used it several times then passed away and it sat until now. Here is what I have done:

    -Cleaned out tank and lines, changed fuel filter.
    - installed new plugs (two sets)
    -removed carbs cleaned them completely, they were not dirty at all.

    Tried starting, ran, but a bit rough. Took it out for a run on my boat ran ok for 15 minutes and then dropped cylinder.#2 cylinder misfiring, pull that plug cap and engine hardly changes, but pull #1 plug cap and it dies immediately.

    Since then:

    -checked plug caps and wires, they are like new. Ohms check on caps OK
    -swapped coils around and problem remained with #2 cylinder
    - swapped out plugs
    - tried different tank with known good one
    - checked timing both #1 and #2 both good
    - checked both coils with meter
    - removed flywheel and inspected charge coil and trigger coils, again like new and checked with meter....ohms check.
    - rebuilt fuel pump, no change.
    - removed carbs and cleaned again.
    - checked all wiring connections a good.
    - compression test both at 120 psi.


    This leads me to believe that the CDI box may be buggered.

    Please help
    Last edited by panasonic; 10-23-2016, 07:36 PM.

  • #2
    If it is getting good spark at the correct time it should not be the CDI because that is all the CDI does.
    did you check spark when it was missing?

    Does it have an alarm warning system on it?
    does it work?
    could it be over heating.

    does it still run on only one cylinder once cooled off?

    If there is good compression and spark at the correct time, then you are left with fuel to air ratio being far enough out that the cylinder is not burning properly
    Seals on crank, carb, intake, reeds, or some where else could be sucking air or too much fuel is getting in somewhere(fuel pump/carb is the only place fuel can be)
    Last edited by 99yam40; 10-20-2016, 06:32 PM.

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    • #3
      Looking for CDI Hitachi TIA02-19

      Hello,

      I am looking for a USED CDI for my 1988 Yamaha 20 HP outboard. The Yamaha P/N is 6L2-85540-10.

      The Hitachi P/N is TIA02-19.

      Please let me know if you have or know possibly where I may find one.

      Thanks
      Last edited by panasonic; 10-24-2016, 12:01 AM.

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      • #4
        Well I guess the problem has been identified...

        Comment


        • #5
          No it has not been identified. I need to try another CDI to rule that out.

          thanks
          Last edited by panasonic; 10-23-2016, 07:37 PM.

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          • #6
            I removed the flywheel again and swapped trigger coils around and the problem remains with #2 cylinder.

            Thanks for input so far...

            Comment


            • #7
              Originally posted by 99yam40 View Post
              If it is getting good spark at the correct time it should not be the CDI because that is all the CDI does.
              did you check spark when it was missing?

              Does it have an alarm warning system on it?
              does it work?
              could it be over heating.

              does it still run on only one cylinder once cooled off?

              If there is good compression and spark at the correct time, then you are left with fuel to air ratio being far enough out that the cylinder is not burning properly
              Seals on crank, carb, intake, reeds, or some where else could be sucking air or too much fuel is getting in somewhere(fuel pump/carb is the only place fuel can be)
              No alarm, yes it will run on one cylinder, with #2 cutting in and out. Not overheating as it does this from cold start right thru to warm up.

              Comment


              • #8
                why do you think the ECU to be the problem if there is good spark on #2 plug?

                a timing light should show if the #2 plug is getting spark and if it is in correct time when problem shows up
                Last edited by 99yam40; 10-23-2016, 04:25 PM.

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                • #9
                  There is no ECU it is a late 1980,s 20 hp!!!

                  Never said that number 2 cylinder has good spark, it is misfiring.

                  Thanks
                  Last edited by panasonic; 10-23-2016, 07:39 PM.

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                  • #10
                    ECU, CDI, the electronics brain.......

                    Have you hooked up a spark tester in the bad cylinder and ran that?

                    Quite a bit cheaper than a spare ECU/CDI..


                    ie:
                    Scott
                    1997 Angler 204 CC, 2006 F150 TXR

                    Comment


                    • #11
                      Originally posted by panasonic View Post
                      There is no ECU it is a late 1980,s 20 hp!!!

                      Never said that number 2 cylinder has good spark, it is misfiring.

                      Thanks
                      Sorry used the wrong term

                      best way is to check spark voltage
                      if you do not have the equipment to read the high voltage to the plugs, then at least read the peak voltages going into the CDI and back out to the coils.
                      when it is miss-firing to make sure there is a problem with voltage causing the miss
                      But that needs special equipment also
                      Last edited by 99yam40; 10-23-2016, 08:51 PM.

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                      • #12
                        Originally posted by TownsendsFJR1300 View Post
                        ECU, CDI, the electronics brain.......

                        Have you hooked up a spark tester in the bad cylinder and ran that?

                        Quite a bit cheaper than a spare ECU/CDI..


                        ie:
                        No I have not.... trying to get my hands on one and thanks for the constructive idea...I appreciate it.

                        Comment


                        • #13
                          Respectfully, I'd start at the point of where you suspect the issue BEFORE you drop hundreds of $ (if you can even find a CDI).

                          IE, New, known good, spark plug.

                          Then get a tester (I also have this one and literally used it yesterday: https://www.amazon.com/Lisle-20610-I...=spark+testers )

                          Crank up the engine and simply watch the unit fire (or NOT). Very visible in the sun light (not as fancy as the other).

                          Confirm spark IS AN ISSUE before going further..
                          Scott
                          1997 Angler 204 CC, 2006 F150 TXR

                          Comment


                          • #14
                            As I said in my last post,
                            read the peak voltages going into the CDI and back out to the coils when it is miss-firing to make sure there is a problem with voltage causing the miss

                            Comment


                            • #15
                              Originally posted by TownsendsFJR1300 View Post
                              Respectfully, I'd start at the point of where you suspect the issue BEFORE you drop hundreds of $ (if you can even find a CDI).

                              IE, New, known good, spark plug.

                              Then get a tester (I also have this one and literally used it yesterday: https://www.amazon.com/Lisle-20610-I...=spark+testers )

                              Crank up the engine and simply watch the unit fire (or NOT). Very visible in the sun light (not as fancy as the other).

                              Confirm spark IS AN ISSUE before going further..
                              Original post stated that the spark plugs where changed out, even bought another set just make sure. Also coils where swapped and trigger coils swapped, and problem stayed with #2. Sprayed fuel into #2 carb and it made no difference.

                              Got my hands on a spark gap tester today and #1 cylinder will jump 1/2" gap easily. #2 on the other hand will barely jump a gap of 1/8" and is firing intermittently, with a weak yellow spark.

                              So with all I have done so far I looks like the CDI is crapping out, nothing else in the ignition system to rule out. I did have a inductive type timing light on it several times and there is enough weak spark to run the light, using a timing light doesn't tell you much about the condition of the spark for sure.

                              Found a CDI on ebay for $150.00 today I hope it solves my problem.

                              Thanks for your input!!

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