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912 ignition issues
Hi all, a while back I picked up an 80 HP 912 that I knew had ignition issues. I figured I would try to sort out the problem before I mounted it on a plane, and so I built a test stand to mount it on. Did that over the last couple of days and this morning it was ready to crank over. I didn't have the chokes hooked up, so I splashed a bit of gas in the carbs and then put the aircleaners back on. It turned about 1/2 a turn and fired off. It did die almost immediately, but I manually engaged the choke on the carb that was closest to me and tried it again. It took off real quick then and ran relatively smooth for no carb sync other than eyeball on the throttle cables and such. It would die on the one mag every time. Swapped modules and such back and forth, and checked other things, and this is what I found out. I had hooked up a tiny tack for an rpm gauge, and so I took another one I had and started moving it from one spark plug wire to the next. I got no reading on #1 and #3 bottom cylinder spark plugs. I would guess that means no spark on them. #1 and #3 bottom plugs both fire off the same ignition module, but different coils. Can a coil be half bad? And then what are the odds of it happening to two of them? Ran out of daylight or I would have swapped plugs to see if I could make it move around, I'll buy some new ones if I can tomorrow. Can the spark plug wires be changed out in the coils, and if so what wire should one get? Thanks, JImChuk
https://www.youtube.com/watch?v=PWTE...ature=youtu.be
Last edited by avidflyer; 09-19-2018 at 07:10 PM.
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Re: 912 ignition issues
Jim
This won't answer your question about changing plug wires but I just wanted to share a website that you might want to look into if you want to get rid of the modules with the short brittle wires. I installed this on my 912 and it works great. I have about 40 hours on it now with no issues.
http://www.sdsefi.com/cpi.htm
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Re: 912 ignition issues
Just a quick update. Today I tried with a timing light, and had nothing on either coil that appeared to only be working on one side. Seems a little power may be going through, enough to get a reading on the tiny tack, but not enough to fire the plug or the timing light. Every thing is a step in the right direction though, kind of like the monkey trying to put different shaped pieces in a certain shaped hole.. I'm the monkey. Now if I could just remember what I tried two times back. Note to self, make notes. I've thought about that other system Paul, could see going with it on one half of the ignition perhaps. JImChuk
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Re: 912 ignition issues
Tried more combinations of stuff today, and module 2 ran coils 3 and 4 with either 4pin connector coming from the engine. Module 2 would not run coils 1and 2. Module 1 ran no coils with either 4 pin connector hooked to it. Tried third module I borrowed from a different 912, and it ran coils 3 and 4 but not 1 and 2. Judging from this, it seems module 1 and coils 1 and 2 have issues. More testing tomorrow. I'll try two different coils and the third module, and maybe I'll have 8 plugs firing. Hope anyway. I'll also check for broken wires on module 1 and the bad coils. I think all the grounds are good, cause I built a new mounting system for the coils and modules and they bolt to the engine and the ground wires are fastened with those same bolts. Progress though. Anything that moves the process forward. Any thoughts on a diagnosis from anyone? JImChuk
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Re: 912 ignition issues
Jim,
I went through a rough time with mine also when I first purchased t. It ended up being a wire that comes up from the stator. It was a bugger to find since it was inside the SS braided line. I found 2-3 breaks in the wire (inside of its insulation) I patched the broken areas but believe I am having the issue again. One module is very intermittent and I may just need to replace that bad wire this time. Unfortunately, I'm going to have to pull the engine off to get to the stator.
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Re: 912 ignition issues
I wonder how hard it would be to replace the wires completely inside the stainless braid? Everyone says the wires break and cause problems, if the wires were replaced with good quality ones, that problem should go away. I know it would be real difficult with the modules, cause if the wire is broke next to or just inside the module, how do you fix that. Different if you can go right to the pick up coil and install another wire. Not sure if that's possible either, but it's worth a try maybe. At any rate, in my case, it seems that the problem starts further down the line, one module and the coils. JImChuk
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