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This post is to report the resolution to a no-start problem on my 912UL.
Background: Aircraft is 2005 DTA Voyageur 2, experimental WSCL LSA, engine SN 4407166, TTSN 330 hr, one owner/maintainer & always hangared. I never attempted to do "spark checks" with the ignition system/plugs etc. not fully assembled or otherwise give cause for an ignition system failure.

Symptoms: Last year, the engine became increasingly hard to start. It either started immediately or did not start no matter what I tried. (RPM was always 350 or more on the aircraft tach.) First I changed the original battery to a more powerful motorcycle battery and kept a battery tender on it. That worked for a while, then I could not start unless I had the tender connected to the battery during start. Then, when that did not work, I tried a new Odyssey PC 680. That did not work, even if using the battery tender during start. I suspected the ignition because all starts were instant, if it was going to start. My checks of the fuel system, carb sync (when I could get it started), and ignition switch showed no problem. I finally got my hands on an IgnitionMate, which confirmed no spark. On the advice of Dean at Lockwood Aviation, I pulled the two ignition modules and sent them in for test. (Thanks Dean.) One was confirmed bad. When I installed the new module ($925 later) along with the other good module, the engine starts every time. I do not understand why replacing only one module fixed the problem since the ignition circuits are independent. I have a key start ignition switch ("off, R, L, both, start" switch positions), so I can not start on only a single ignition circuit. However, when I check each circuit immediately after start, they are both working.
When I searched the Internet for others with this problem on a 912 UL, I found only one other instance. The resolution was the same although discovered by chance: one new ignition module fixed the problem. There is much counseling on the Web that 912 start problems are almost never ignition problems. Hopefully this post will help someone with a 912 start problem be a little more suspicious of the ignition.
  • Re: 912UL no-start resolution

    by » 11 years ago


    Robert,
    Just a thought here, your starter switch, (off,r,l,both,start) is based on a Bendix switch and it may be a Bendix. Anyway, on the terminal end of the switch, one of the posts can have a jumper on it to the ground terminal and it will kill one mag when the switch is turned to start and keep it killed until the switch is released to both. I can't remember offhand which mag it kills and you may be able to kill either mag during the start. I forget now (getting quite often anymore) why this was done, it was either for a "shower of sparks" device on some planes or to disable the mag with no impulse on the magneto. Again I just can't remember now.

    Is it possible that this jumper is on the back of the switch? This may cause the problem you are having by killing the good box and it trying to start on the bad box. This jumper will go from one terminal to a terminal in the center (ground).

    Dale

  • Re: 912UL no-start resolution

    by » 11 years ago


    Robert,

    Pull up this page http://www.aircraftspruce.com/catalog/elpages/ignitionswitchkit.php it gives a diagram of the terminal on the rear of the switch. Terminal 1 for the right mag is the one where the jumper goes. The two terminals are close together and the jumper goes between these two terminals and not to ground as I stated earlier(it does ground the right mag internally though). Also make sure these two terminals art not loose and touching each other.

    Dale

  • Re: 912UL no-start resolution

    by » 11 years ago


    Dale, thanks for the reply. The diagram looks like what I have, without pulling out the switch to be 100% sure. I can say with assurance there was no jumper. I did not notice anything unusual during inspection wrt contacts loose or touching. Good thoughts however.
    Bob

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