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Dick Maddux
Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl
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 Posted: Thu Sep 25, 2008 4:48 am Post subject: Bad mag check 912UL |
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I have a 912 UL on my Kitfox and have had a persistent problem I can't seem to pin down. The right mag is having a persistent drop of about 800 rpm running rough and the engine is even quitting (when mag switch is in right mag only)
I have an elderly engine with the A module on top.( 180 hrs tt) When I wiggle the 4 pole plug receptacle and the red power wire then I will get my mag back for a little while (until I start it again and do the runup then it will misfire again. I have stripped back the short black wire protective cover at the module and have slit open three of the wires I found "kinked" expecting to find breaks but they were all intact. This morning I am going to reinstall the plug and try trouble shooting the red module power wires.I have already replaced the "p" leads and the mag switch.( they check good with an ohmeter)
Is there any way to test the wires for a break (or breaks) without running the engine? Electric's are my absolute weakest area and I am having a real struggle with this.
Any ideas? Am I going down the right trail?
Thanks
Dick Maddux
Kitfox 4-1200
Rotax 912 UL
Pensacola,Fl
Looking for simple solutions to your real-life financial challenges? Check out WalletPop for the latest news and information, tips and calculators.
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Thu Sep 25, 2008 4:57 pm Post subject: Re: Bad mag check 912UL |
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Hi Dick,
You can do an ohm meter check through the wires from the coils to just before to module. This will tell you if the coils are ok. I don't have a manual handy so I don't know what the values are. This doesn't sound like a coil problem. Is your engine old enough to have just one ignition module? It sounds like it could be a bad wire in the plug socket just before the module. IF you can wiggle the wires and they work then you most likely just have a bad connection and possibly in the socket. At an 800 rpm drop you are losing one complete ignition bank or 4 plugs. You can get an AC power tester for about $12 and since the plugs produce AC power the tester will show you which wires from the ignition coils to the plugs are firing and which are not. Picture attached. This tester can also find bad plugs and plug wires if you are only dropping 300 rpm. You just need to get the tester near the wire or touch the wire. If the module is bad wiggling the wires should not help. That's why I think it is just a bad connection since you can wiggle the wire and make it work until vibration loosens the connection again.
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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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Dick Maddux
Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl
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| Posted: Fri Sep 26, 2008 4:46 am Post subject: Bad mag check 912UL |
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Roger,
Thanks for your reply!
Yesterday I switched the red power wires from the coils to the modules and found the problem went with the wires (ie: now the left mag vs the right mag was acting up and the engine quitting) I then took my ohm meter and measured both the right and left red power leads. I measured 5.7 ohms on the left and " 0 " on the right so as you said, I should have a break in that wire. Now the problem was--- where? The wire looked fine.The break could be at the back of the engine (oh boy, pull the engine as it is a tight fit on my Kitfox) I took a chance and I connected one of the alligator clips to a sharp tipped scribe and worked from the connector end (at the top of the engine) down the wire pushing it thru the wire insulation. At about 3/4 inch from the female connector end I hit paydirt ! I was registering 5.7 or so on my ohm meter !!!
Now this piece of wire looked absolutely solid and you could not feel the break with your fingers. After careful surgery on the wire I could see most of the strands had been broken for awhile (by the color of the ends)
I spliced in a fresh piece of wire and was able to reuse the connector end. The module is now working and I am back in business!
I can't thank you enough for your insight as you were on the money. Another learning experience on this strange engine! I wish someone would make up a full color wiring diagram that is easy to read (and large enough) I bought one a few years ago for my Triumph TR3 and Stag off of a guy on EBAY.It sure makes it easy to follow the wiring. I think I paid about$20- 25 apiece. It was sure worth it!
Dick Maddux
Kitfox 4-1200
Rotax 912UL
Pensacola,Fl
Looking for simple solutions to your real-life financial challenges? Check out WalletPop for the latest news and information, tips and calculators.
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| | - The Matronics RotaxEngines-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Fri Sep 26, 2008 12:55 pm Post subject: Re: Bad mag check 912UL |
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Hey Dick,
Good job. You did it the only good way to track down a ghost in the wiring, inch by inch sometimes. Typically wire breaks happen at plug connectors or sharp bends around something.
Happy flying! 
| | - The Matronics RotaxEngines-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RotaxEngines-List |
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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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