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Start up problems

in 912 / 914 Technical Questions 7 years ago
Good day

I have a 914 UL engine that struggle to start after the aircraft was not flown for approximately 5 days. The problem is not petrol related. After 5 days when the aircraft is started you have to crank the engine sometimes for more than 20 seconds and then suddenly the engine starts up. After the engine has been started the following day the engine will start without any problems. After the aircraft was not flown for 5 days or more the same start up problem develop. I replaced the battery with the same result. Mags test is 100% when tested.Can someone help me on this topic.

Regards

Mossie

  • Re: Start up problems

    by » 7 years ago

    Is this a new development or something that has always been there?

    Make sure the plugs are gapped properly, but I think it is a fuel delivery problem and or a starting technique problem. You may have fuel draining away from the carbs and or the top fuel hose system. You need to make sure the choke (enricher) system is operating properly and you use full choke to start. If your idle is set down around 1700ish then make sure to crack the throttle on ta first start so when it does fire the rpm is around 2000-2400.
    The other side of this coin could be flooding of the carbs. You will have to rule in or out all these above. If you keep cranking the engine for those long periods you will burn up a starter and or ruin the sprag.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Start up problems

    by » 7 years ago

    This may also be the ignition modules on their way out. They can be very temperamental when they are about to give up, and once the engine has started they can be fine for a day or so until left and then they may not work again.

    If you have access to another engine, either 912 or 914, that you can borrow the modules off to test, it may be worth doing.

    I think this would be my first port of call.

    How old is the engine?
      
    Report

  • Re: Start up problems

    by » 7 years ago

    I thought about the modules, but the 5 day issue made me think different.
    Hard to start one day, but starts just fine the next. It is only hard starting when it sits 5 days.


    You may only have to take the calendar away from the modules. LOL
    Sorry Mark I couldn't resist.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
    Report

  • Re: Start up problems

    by » 7 years ago

    Hi Roger

    Thanx for the reply. We made sure that there is adequate fuel in the carbs before start up by switching both fuel pumps and chokes. As I said once it has started the following days it starts with no problem with the first swing of the engine. The problem only pop up after the engine stood for 5 days or more. I am also suspecting the ignition modules as the aircraft was based at Cape Town for most of its life and maybe the ignition coils got some rust or dirt cover on it.
    Regards

    Mossie
      
    Report

  • Re: Start up problems

    by » 7 years ago

    Hi Mark

    Thanx for the reply, I will try to get hold of ignition coils and hopefully it is the problem. We also got some advise from an AMO that if the engine turns over a fraction to slow that the ignition coils will not generate enough power to ignite the coils. We however made sure that the battery is up to 13.6 V before we crank the engine but still no luck. I still have to establish at what rpm the engine have to turn over to create enough power to ignite the coils the eliminate the starter motor as the problem.

    Regards

    Mossie
      
    Report
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