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Cold starts are easy; warm starts are impossible

in General Tech Discussion 12 years ago

  • Re: Cold starts are easy; warm starts are impossible

    by » 12 years ago

    8 hours, 6 minutes ago #3156
    Roger Lee
    Getting the idle rpm set up to 1700-1800 rpm will help on your starts and keep from beating up your gearbox.
    Unless you have done a slipper clutch friction torque test on the gearbox and it shows low it doesn't need to be re-shimmed. Re-shimming is done if your gearbox friction torque is low. If it is low then you may be experiencing kick back at the prop during stat up. Fix the idle rpm first. Make sure the choke circuit is not engaged after it is warm when you try to re-start. Normal and average friction torque is usually between 440-485 in/lbs.

    Hi Terry

    As you have said in your earlier post that you don't have have a slipper clutch, then you can't check your friction torque as it does not exist on your gearbox.

    Trust me, if your engine has been idling for a couple of hundred hours at 1200 rpm the your gearbox will need re shimming.

    Cheers Mark
      
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  • Re: Cold starts are easy; warm starts are impossible

    by » 12 years ago

    Hi Mark and Terry,

    I missed the comment on the UL part and no clutch. I was thinking ULS. My error.

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

      
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  • Re: Cold starts are easy; warm starts are impossible

    by » 12 years ago

    Well guys, this is the latest! I was at the airfield this weekend and we messed around with the plane. We have redone the carbs, replaced the electronic ignition module, checked all ignition leads, tried a new battery, flushed out the fuel system and all of your other suggestions. Thanks you by the way!

    Over the last week (during testing) the mechanics have had the devil's own job getting the engine to start at all (even when cold). Same problem; engine fires and thrashes around but will not pick up when throttle is advanced. we finally got it started and then tried warm starts. We found, by advancing the throttle about half an inch, the engine fires immediately and sounds really sweet. Pulling the throttle back to idle immediately (once the engine has fired and is turning over)continues to give a smooth idle. Apart from this, the engine runs perfectly throughout the rev range.

    I'm quite happy with the fact i can now start the engine however, opening the throttle half an inch on a crowded ramp is not something I am all that keen on.

    Lastly, we have been using 100 octane fuel. I have just found out the manufacturer puts acetone in the fuel (this is what I was told) to boost the octane rating. Any thoughts on using 93 or 95 octane fuels even if they have 10% alcohol?

    Thanks again for all of your help
      
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  • Re: Cold starts are easy; warm starts are impossible

    by » 12 years ago

    Hi Terry,

    The 91+ octane auto fuel with or without ethanol is absolutely the better way to go compared to 100LL. The engine doesn't care about the ethanol, but make sure your fuel tanks are okay with it.

    Did this hard starting happen before any maintenance and out of the clear blue? Did it start fine one day and then the next have this problem?
    If any maint. was done prior to this what was it

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

      
    Report

  • Re: Cold starts are easy; warm starts are impossible

    by » 11 years ago

    Hi Roger- 1st time I've posted to this list, but see the depth of your knowledge in your postings . I have a hard-start issue with my 1995 912UL. It has only 170 hours on it, has always started first blade, warm or cold weather (in Florida.) All of a sudden it doesn't start when the normal procedure is followed: burp oil tank, master on, both mags on, choke on, engage starter, (engine starts immediately.), choke off. Frustrated, I used engine starter spray can- very light spray on each air filter (you probably don't approve of that.) Voila! immediate one-blad start. (battery is fairly new and always on a maintenance charger, turns if over briskly.)

    Then all restarts during the day thereafter are normal- one blade. That makes me think I don't have any fuel flow problems... or ignition system problems... but that doesn't leave anything to be the problem. This just started out of the blue- not after any maintenance. It's in a Kitfox, gavity flow with header tank, old-style mechanical fuel pump, no electric fuel pump, no Bully Soft Start module. Never the slightest kind of problem starting in the past. Any ideas?

    Thanks. Ben Burbridge
      
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