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RPM LOST ON IGNITION CHECK

in 912 / 914 Technical Questions 7 years ago
Hello,

While making the check of the ignition on the number 1 (A module), I have a 800 RPM lost only when the engine has been stopped after a flight or the aircraft has been parked outside in a sunny day therefore resulting within the engine cowl a hot ambient temperature. It's working well at the first flight of the day when I get out the aircraft from the hangar !

I have change the DUCATI Electronic Module with no result. I have change the ignition coils on the ignitor circuit A with no result. Does anybody has an idea what to do to solve my problem ?

Best regards,

  • Re: RPM LOST ON IGNITION CHECK

    by » 7 years ago

    "I have change the DUCATI Electronic Module"

    It is not a Ducati. Did you put in a Rotax ignition module?
    Since changing the module didn't help:
    You most likely didn't have a real ignition module problem, but only a bad wire. Check the red wire on top of the engine to the modules, Really do a good check on the wires into the 6 pin connectors for breakage at the pin inside the plastic connector.
    Did you try swapping the modules at the 6 pin connectors and see if the problem stayed the same or changed? You can ohm out some of these wires to their sources, but do these simple checks first. Most problems aren't exotic, but simple fixes. Start there first.

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

      
    Report

  • Re: RPM LOST ON IGNITION CHECK

    by » 7 years ago

    Hello Roger,

    Thank you for your prompt reply. The modules on my ROTAX 912ULS, mounted on my CTLS, are the original's one made by DUCATI.

    At the begining, I swapped the pin connectors and had the problem on the other module. That's why I incriminated and changed it.

    I will have a look on the wire and keep inform you about the result.
      
    Report

  • Re: RPM LOST ON IGNITION CHECK

    by » 7 years ago

    These aren't Ducati modules.

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

      
    Report

  • Re: RPM LOST ON IGNITION CHECK

    by » 7 years ago

    Please, visit the following web site to see what is installed on my engine.

    https://www.carmo.nl/index.php?main_page=index&cPath=493_4686_2711_4618&language=en
      
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  • Re: RPM LOST ON IGNITION CHECK

    by » 7 years ago

    My ignition modules have Ducati embossed on the outside of the cases :-) They may not be made by Ducati but they certainly have their name on them.
    I've just had 2 modules fixed by Carmo, their service was excellent and quick. One had a faulty kill input, the other wouldn't fire at cranking speeds when cold. Both are known faults with these modules. You've only got to speak to the guys at Carmo to see how common it is.

    Test results:
    1. You have an 800rpm drop when you switch off module A when the engine is hot.
    2. If you swap both of the connectors then the fault moves to the other module.
    3. Replacing module A does not fix the fault.

    Conclusions:
    1. If switching off module A results in a large rpm drop then the module B circuit/module must be at fault.
    2. If swapping the connectors moved the fault to the other circuit (ie. switching off B circuit results in 800 rpm drop) then fault is in B circuit not module.

    The ignition circuit consists of:
    1. Trigger coils. (cannot cause observed symptoms)
    2. Charging coil.
    3. Coils.
    4. HT leads & resistive caps. (cannot cause observed symptoms)
    5. Spark plugs. (cannot cause observed symptoms)
    6. Earth connections to manifold.

    Given that you have already changed the coils then I would look at the charging coil and the earth connections. You could use a voltmeter to measure the charging voltage on the red wire to each module, they should be about the same. I have some oscilloscope traces which look like they would give you about 50-100V AC at 3000rpm.

    Another thought is that you could measure the resistance of the charging coils with the ignition modules disconnected and heat them up with a hair dryer to see if one changes more than the other. Good luck!
      
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