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1989 johnson gt 150 - all electric components tested working , wont start

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  • #1

    1989 johnson gt 150 - all electric components tested working , wont start

    Hey All,

    I am new to this forum as a member, tho have been reading on various johnson motors for about 3 months now.

    I have an old 1989 Johnson GT 150 motor i am working on that sat for about 6 years. i started with a full tear don on the carbs, water channels, fuel tank and various other components. Motor would not start, but replaced the power pack (tested & failed) and the timer( tested and failed). Removed the flywheel and found the stator to be burnt and melted, black goo all over motor. While i was there and replacing 3 major components i decided to do the rectifier/regulator as well.

    Flash Forward to new fuel lines, pumps, and parts - motor started right up, tach moving smoothly.

    I then found a small fuel leak from the middle carb and pulled it to fix.

    reinstall. prime ball. level motor. hold in the choke several seconds. and all i get is a several back fires and then none at all. motor spins freely and even exhaust flow from prop, but fails to start. the packs have been tested and replaced(1) an the plugs all new champions, tho when pulled were pretty rich, cleaned and reinstalled.

    Anyone have any ideas? the kill switch is not an issue, it is disconnected. i have even disconnected the red plug and jump over the solenoid to start the engine, still nothing.

    Thanks for your time, any suggestion would be appreciated as motor ran, but wouldnt after simply removing carbs and reinstalling to seal a fuel leak from the low connection on the ball
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  • #2
    Presently.... all spark plugs removed. Check the compression, what is the compression psi of all the individual cylinders?

    S/plugs still removed.... Do a spark test. The spark must jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?

    Please do not come back with a reply with something like... the compression is good all the way round and the spark is great! This means nothing to us, be specific.

    The flywheel nut must be torqued to 145 foot pounds. Anything less will result in a sheared flywheel key, throwing the engine out of time, and damaging the taper of the flywheel and crankshaft.

    Now... if you have proper compression and spark, and the engine refuses to start, the cause is usually fouled carburetors. However it could be that the engine is cranking over via the electric starter too slowly... it must crank over at least 300 rpm to energize the powerpack... or perhaps you are not engaging the fuel primer solenoid? But first start with the basics as mentioned above.

    What brand spark plugs are you using, and what are their designations? THey should be Champion QL77JC4 plugs gaped at either .040 (strong spark) or .030 (long life).

    Let us know what you find.

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    • #3
      Currently using the Champion QL77JC4 plugs gaped at .030 - this was what the factory manual said so not knowing better i went with it! As far as spark, compression - i will be doing this tomorrow. I went ahead and took the carbs off for a rebuild.

      as far as spark, use an inline tester?

      and for the flywheel, 145 foot pounds of torque, i threaded it back on by hand, then used a wrench while having a friend hold the flywheel, then an electric impact. i have an air impact running 120psi i can hit it with again. I was cautious as the past nut was a bare to remove and didnt wanna strip this one

      Thanks for the input!

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      • #4
        I strongly suggest that you do not use an air impact wrench on that flywheel nut. The 145 foot pound torque that nut requires will absolutely shear on anything less... and if over-tightened, you risk the spreading of the flywheel taper (Not Good!).

        If you have proper compression and spark... BUT... the engine backfires out the exhaust (shotgun noise type backfire)... the flywheel key is no doubt sheared, will require replacement, and the tapers of the flywheel and crankshaft will need touching up.

        If the key sheared, purchase the proper recommended key... NOT one purchased in a hardware store that looks similar. The key is to be installed with the flat outer edge straight up and down, in line with the engine... NOT in line with the crankshaft taper.

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        • #5
          new key(oe) purchased, old one sheared... thank you for the info! cleaning up the tapers?? is the taper directly below the flywheel nut threads?

          what is the protocal for reinstalling the flywheel ? can i use a torque wrench set to 145 ft lb ?

          Thanks!

          Comment

          • #6
            Originally posted by kknopp01 View Post
            new key(oe) purchased, old one sheared... thank you for the info! cleaning up the tapers?? is the taper directly below the flywheel nut threads?

            What is the protocol for re-installing the flywheel ? can i use a torque wrench set to 145 ft lb? Thanks!
            Remember... the straight edge of the flywheel key must be straight up and down, NOT aligned with the crankshaft taper!

            Yes, the taper is the angle of the crankshaft directly below the threads. The taper of the flywheel is obvious.

            Yes, in fact you MUST use a torque wrench set to 145 foot pounds.

            To keep the flywheel from turning... use what the auto mechanics use to turn a automobile flywheel when installing a standard shift clutch and pressure plate. It's called a Spanner Wrench as pictured below.

            Comment

            • #7
              Thank you! i reinstalled parallel as u stated! flywheel back on, bolt torqued to 145. Now onto my finally issue, setting the timing, starting a new thread if anyone can help with that!

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