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I'm stumped with a lack of spark on my 912UL, and have spent several hours on the forum reading the many ignition related topics and now 5 days troubleshooting. I'm completely stumped and would really appreciate any help.

Quick Background Summary: Recently purchased a Kitfox 4-1200 with a 912UL SN: 4152052 that had a "hard to start" issue which the owner disclosed and suggested was a carb sync issue. That was likely not accurate, as the carbs were overhauled by Lockwood within the past 25 hours. I flew the plane 3 hours home (even encountered a heavy rainstorm) and the engines never missed a beat. Landed at my home airport near St. George, Utah and have never been able to get the engine started again.

Remedial work performed: Discovered that a Service Bulleting to replace the stator had never been accomplished and there was significant abrasion through the shielding, along with frayed wires supplying power to the CDI. I purchased and installed a new stator and while the engine was off, decided to also replace all the trigger coils. I also replaced old Ducati CDI boxes with the Sportflight CDI's (aftermarket).

Results: With a good strong battery, and the soft start feature installed, I turn over the engine and there is no spark on either channel.

Troubleshooting: Doubled checked all connections (had to remap the trigger coil leads into a six pin plug). Provided three independent ground connections to ensure there was no lack of grounding. Measured a steady 18 VAC output from the red stator ignition leads. Also had to replace one ignition coil as the input lead pulled out during the rewiring.

I realize that a change of so many components makes it more difficult to pinpoint the issue. 

Thanks in advance for any suggestions on troubleshooting.

  

 


Model IV-1200 Tricycle Gear w/ Speed Wings

RV4 in Progress

  • Re: Ignition System Troubleshooting - 912UL

    by » 3 months ago


    I'm not familiar with the Sportflight CDI modules and I cannot find any details online. I suspect that they are similar to the Ignitech modules that have built-in soft-start and an auxiliary 12V power supply to aid starting.

    Given that you have changed so many components there is a lot to check through to see where the problem lies. You may have done some of the following but here are some thoughts:

    Remove all the top spark plugs and position them so that you can see the electrodes of the top plugs and that the plug body is in contact with the engine body.

    Refit your old CDi modules and crank the engine. Any spark?

    Refit one of your old trigger coils and connect it to the CDI module. Crank the engine, look for a spark.

    If you still don't have any luck, then visually inspect the new stator and rotate the engine by hand to ensure that the timing tabs pass the trigger coil poles correctly and the gap is as per the heavy maintenance manual.

    Make sure the kill switch inputs are not grounded.

    There are a number of resistance measurement specified in the manual which would be worth verifying.

    All you need for a spark is: power to the CDI either through the stator coil or the aux 12V on the replacement CDI, a pulse of large enough amplitude on the coil trigger input, a correctly connected coil and a spark gap.


    Thank you said by: DAVID R WALKER

  • Re: Ignition System Troubleshooting - 912UL

    by » 3 months ago


    Hi all

    First a few basics.  The CDI generates its own spark without input from a battery.  It however will require at least 225 to 250 crankshaft speed to maintain charge in the capacitor between trigger signals.  The standard 912 has a cross fire in that the A, top module, fires top 1 and 2 cylinder plug plus bottom 3 and 4 plug.  B fires the others.  

    The trigger gap is sensitive and must be correct for the trigger type used (see heavy manual) Too large a gap and it will not fire.  Adjust as needed.  

    Confirm with a good auto range meter that all ohm readings per the heavy manual are correct.  Confirm all grounds (the most common cause of problems)  

    I have no data on the aftermarket parts so you must contact them however it is unlikely that both of the original ones failed at the same time.  

    Also do not discount problems with the spark set or the connectors.  Be sure to check the high tension wires also.  (in the list of items to inspect from the heavy manual) 

    Cheers

    PS, when cranking to view a spark on a CDI the spark is very short and difficult to see in bright light.  Do this inside or in a shaded or dark area.  Confirm with an optical tack that you have 250 RPM at cranking (100 RPM on the prop) Take care ot be sure that the plugs are grounded so it will not backfeed and damage the capacitors inside. 


    Thank you said by: DAVID R WALKER

  • Re: Ignition System Troubleshooting - 912UL

    by » 3 months ago


    All 

    From heavy manual, ohm checks.  

    Cheers

    38504_2_ignition checks 912 914.jpg (You do not have access to download this file.)

    Thank you said by: DAVID R WALKER

  • Re: Ignition System Troubleshooting - 912UL

    by » 3 months ago


    I've done most of these steps, but will go back and verify my work. I have not carefully OHM checked each of the components and that will be my next step. I also have a set of known-to-be-working Ducati CDI's lent to me by a buddy which I'll reconnect and test next. 

    Is there a signal check for the trigger coils? Restated, is there a way to verify the signal by cranking the engine and reading a voltage drop or surge? The OHM readings are all good, and I set the gap at .14 (.12 - .16 is what I remember seeing in the HMM).

    In a separate post, during the rebuild I was concerned about the position of the trigger coils relative to the flywheel tabs.

    Thanks again for the suggestions!

      

    38508_2_stator.jpg (You do not have access to download this file.)

    Model IV-1200 Tricycle Gear w/ Speed Wings

    RV4 in Progress


  • Re: Ignition System Troubleshooting - 912UL

    by » 3 months ago


    Hi again David

    Given you are in the USA I might suggest you remove all the ignition and send it to an overhaul facility to have testing done on a live bench.  If you have done all the ohm tests and physical tests then i would certainly think that would be prudent.  I know Lockwood Aviation has a bench and coordinate with them on what they would like back.  That is the only "live" way to check any of the parts.

     

    Cheers


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