Kitfox Aircraft Stick and Rudder Stein Air Grove Aircraft TCW Technologies Dynon Avionics AeroLED MGL Avionics Leading Edge Airfoils Desser EarthX Batteries Garmin G3X Touch
Page 1 of 6 12345 ... LastLast
Results 1 to 10 of 53

Thread: Ignition Gremlin

  1. #1
    Super Moderator Av8r3400's Avatar
    Join Date
    Jan 2009
    Location
    Merrill, WI
    Posts
    3,044

    Default Ignition Gremlin

    As I alluded in the "Milestone" thread, I have been chasing an ignition problem in the Mangy Fox ever since the first start. Because of this, the flight testing has been put on hold.

    Here is a description of the problem:

    On doing the run-up to 4000 rpm, testing one ignition (A) will drop about 50 rpm. Perfect.

    Testing the other ignition (B) gives ~500 rpm drop and the EGTs (located on cylinders 3 & 4) quickly climb through 1500º! Not so perfect.

    I have done all the usual stuff.
    • Cleaned all grounds
    • Checked firing order
    • Cut the tips off the plug wires and inspected boots
    • New Plugs Gapped to .027"
    • Removed modules and checked wiring
    • Removed, cleaned, rebuilt, synchronized carburetors
    • Then I did it all again...


    I spent time today speaking with tech support with CPS, LEAF and Lockwood. The guys at Lockwood cam up with the theory (and they have seen this before) that one of the modules is malfunctioning and could be firing one side 180º off. This would cause the problem I'm seeing.

    Each module fires a coil every 180º of crank rotation and each coil fires a pair of plugs (1 & 2 top, 3 & 4 bottom, etc.). If the module is malfunctioning and firing both coils at the same point, then one pair of plugs will ignite the fuel on the way out the exhaust valve, causing the EGTs to skyrocket.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  2. #2
    Super Moderator Av8r3400's Avatar
    Join Date
    Jan 2009
    Location
    Merrill, WI
    Posts
    3,044

    Default Re: Ignition Gremlin

    I sent the modules off to Lockwood today to have them tested. (Lockwood is the only place in the US with the testing machine for them)

    I have mixed feelings on this. If the module is bad, it will cost me $1200 for new one. If the modules are good then I've got absolutely no clue what's wrong. (But I'll still have money in my account) That's either a win-win or a lose-lose, I'm not sure...



    I've heard that kidneys are selling for about $1500 these days.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  3. #3
    Senior Member HighWing's Avatar
    Join Date
    May 2009
    Location
    Goodyear, AZ
    Posts
    1,743

    Default Re: Ignition Gremlin

    "Checked firing Order". Not sure what this means. Would this check have detected the 120 degree off Lockwood is suspecting? The first thing that came to my mind is the possibility that the 1 - 3 or the 2 - 4 lower plug wires might have been switched. Do you have the yellow tags on the ignition wires?
    Last edited by HighWing; 03-02-2016 at 07:33 AM.
    Lowell Fitt
    Goodyear, AZ


    My You Tube Channel

  4. #4
    Senior Member
    Join Date
    May 2011
    Location
    MN
    Posts
    469

    Default Re: Ignition Gremlin

    Not sure if this makes much differnce, but I thought the plug gap was supposed to be set around 0.021". I need to go check my Zipper plugs I guess.

    I just seem to recall there was a 'tighter' gap with one of the piston sets. I do recall the 95 HP Extra-Performance pistons suggested a smaller gap than factory.

  5. #5
    Super Moderator Av8r3400's Avatar
    Join Date
    Jan 2009
    Location
    Merrill, WI
    Posts
    3,044

    Default Re: Ignition Gremlin

    When I say check the firing order, I mean the routing of the plug wires to the proper coil. That also means checking that the coils were wired properly to the correct ignition module wires and the plugs were hooked to the proper coils. Thus eliminating the possibility of 1/3 and 2/4 wire mix ups.

    Rotax calls for .028" gap on plugs.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  6. #6
    Senior Member
    Join Date
    May 2011
    Location
    MN
    Posts
    469

    Default Re: Ignition Gremlin

    Yes sir, it was the plugs on the 912 XtraPerformance pistons I originally had in the motor that needed a smaller gap.
    www.craftworks.biz/pistonsite/6318.htm

  7. #7
    Super Moderator Av8r3400's Avatar
    Join Date
    Jan 2009
    Location
    Merrill, WI
    Posts
    3,044

    Default Re: Ignition Gremlin

    It's a Good news - Bad news situation today.

    Good news is that the modules checked out fine down at Lockwood.

    Bad news is now I have no idea what the problem is…
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  8. #8
    gregsgt's Avatar
    Join Date
    Aug 2013
    Location
    Binghamton, NY
    Posts
    101

    Default Re: Ignition Gremlin

    The EGT climb doesn't make sense to me. Dropping a mag should make the mixture more rich and EGT's climb when the mixture gets lean...

    I think it sounds like a wiring problem in the ignition somewhere. Maybe a bad switch or something.

  9. #9
    Senior Member Slyfox's Avatar
    Join Date
    Dec 2008
    Location
    felts field, spokane
    Posts
    1,327

    Default Re: Ignition Gremlin

    this is my thoughts. when you get your modules back, switch sides, see if it changes to the other side, if not, electrical wiring
    steve
    slyfox
    model IV 1200-flying
    912uls
    IVO medium in-flight
    RV7A-flying
    IO-360
    constant speed prop

  10. #10
    Senior Member Dave S's Avatar
    Join Date
    Oct 2008
    Location
    St Paul, MN
    Posts
    1,833

    Default Re: Ignition Gremlin

    Larry,

    Don't know if this would help any; but, on single ignition engines timing can drastically affect RPM. If everything else is equal (thottle the same) advanced timing will result in a higher RPM......retarded timing will result in a lower RPM...retarded timing taken to the extreme (short of killing the engine) can also result in a big RPM reduction with the charge burning partially on the way out of the engine which would possibly raise the EGT.

    When you mentioned 50 and 500.....the 50 almost seems like less of a drop than a person would normally get on Rotax. If considering timing....is there any chance that the side which drops off 500 and raises the EGT is running on a severely retarded timing setting?

    I don't have a clue how timing is controlled on a Rotax. Don't recall if you have the soft start (which I believe retards the timing to prevent kickback) and I don't have any idea if there is any possibility of the soft start affecting the running mode.

    Again, not saying that I know anything about what the problem is; but, thought I wanted to share this possibility in case it might play into the issue.

    Wish you luck in solving this.

    Dave S

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •