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Ign. not fixed


procharger

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Checked all connections with meter, checked all trigger coils, checked plug

connections to trigger coils with meter, all check good, checked red wires

to modules, put old modules back on still can't get 3&4 on top and bottom

to fire either fires on top or switch plugs on modules it fires on bottom, closed

gaps to .012 on trigger coils, checked all ground to coils can't find anything

wrong. hooked up clips to plugs from trigger coils to see if all are getting

voltage when cranking engine, meter shows them all sending voltage to

both modules. One coil was reading a  little lower then the other 3 but

not by much.

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That's *very* significant actually.

 

Also, what kind of high tech voltmeter? I doubt you are going to see the peak voltage if it's nothing short of an oscilloscope or circuit analyzer built in because the transient voltage will be so fast. It is a CDI ignition after all.

 

If you've been switching modules to test and that's been going on, then it's definitely a clue. I assume you checked across the coil? If so, that means the coil isn't dropping the voltage it's supposed to (and feeding the other .8 volts back into the module... BAD BAD BAD!), so it's very possible it's a bad coil. Or, you just happened to have checked just after a bad spot in the connector, and that connector was dropping the .8 volts, and the coil was dropping the other 3.7...

 

Did you say switching the two modules still had the same two bottom plugs inop? If so, your trigger coil kit and messing with the modules will do nothing, it's either on the coil side of the connectors, distribution wires, bad ground for the coils, or a bad coil itself (despite what your dr rotec says).

 

Let's even treat the top set of plugs and bottom set of plugs as two different issues. When we do that, it makes so much more sense (two coils going bad at roughly the same time). It's the only thing that makes sense, actually, unless someone screwed up your ignition wiring badly.

 

You should try switching 2 coils. See if the problem follows it.

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Like I said getting desperate, the only thing that was touched during the sprag

install were the trigger coil and we had to move the wiring and harness around

on order to remove and install mounting frame it was running fine before all that

no coils was touched so I am hoping somewhere during that a wire or something

got damaged maybe inside harness I will let you no what happens. I know we

can't read actual voltage from coils but we are working on it at my hanger out in

farm country using what we have to work with. thanks we have switched coils same

result.

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So despite switching them, still no spark on bottom plugs? Did you just switch which plug leads go where, or did you also change the individual pins in the connectors too? (Just moving the coil to another position won't do anything).

 

Also, try meggering the spark plug leads. I am curious if the insulation decayed and the spark is escaping.

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Wait wait, I just thought of something. I just looked up typical CDI ignition circuits, and noticed a very critical difference from magneto circuits... The primary and secondary sides are completely isolated in CDI, while in magnetos, I know they share a common. This difference presents a new possibility...

 

There are only two leads going to the coils, and 2 wires coming out to each plug. If, and I mean IF, this CDI similar to the same as the diagram I am looking at, it might mean the spark goes out one lead, through the plug, through the case, through the other plug and lead, and back to the coil. But, I could be talking out of my rear end and it might go back to the coils through the coil mounting hardware, so take that with a grain of salt.

 

Sooooo, make sure that when testing for spark, BOTH plugs have a good connection to the case!

 

You can probably check this theory with the secondary side by checking continuty, just touch inside of both plug boots on bottom 3 and 4, assuming your ignition isn't hooked up wrong. Then check from boot to mounting hardware for the coils to see if there is continuity there as well.

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I meant if the pins are not in the correct place in accordance with the wiring diagrams in the maintenance manual, or if the wrong plug wires are going to the wrong modules... that kind of thing. It can make remote troubleshooting a lot more difficult.

 

Also, I just pulled a set of coils out that I had setting around. My theory is correct, the secondary loop goes through BOTH spark plugs, and I'm not seeing any sort of common on the primary wires side, nor via mounting hardware. Next time you check for spark, make sure that you have solid connections on both or the circuit will not complete.

 

This would explain why you might have issues with the top plugs too, if you tested them and you just left them dangling, it might not have had a connection.

 

And before anyone asks: yes it means that one bad plug means the other will not fire either. No, it's not exactly an ideal setup, but it's far from "unsafe". A double failure of a top and bottom plug would be extraordinary, let alone a quadruple failure of 2 more plugs, on the other two coils, on the other cylinders.

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Swap the 2 module plugs going to the ignition transformers, (the ones with the sparkplug leads), did that change which sparkplugs are firing?

If the answer is yes, swap the 2 module plugs going to the trigger coils. Did the change back to the original plus that were firing?

If yes your problem is with the trigger coil or wiring from the coil to the plug.

 

I think this will help you get on the right track.

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I'm familiar with the two "ignition modules" which are stacked on top of one another and located near the airbox and the 4 "ignition coils" which have the secondary plug wires running from them to the plugs.  Are the "trigger coils" located in the stator assembly on the back of the engine?

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I'm familiar with the two "ignition modules" which are stacked on top of one another and located near the airbox and the 4 "ignition coils" which have the secondary plug wires running from them to the plugs.  Are the "trigger coils" located in the stator assembly on the back of the engine?

 

Yes, they are what tells the module when to fire the ignition.

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Thanks Tom.  The manual calls out part #9 for these coils but I could find these in the picture.  It looks like the engine must come off the plane to get to these coils?  If so, is there a diagnostic procedure one can perform after repairs are done and prior to installing the engine which would indicated all is working OK?

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It requires an oscilloscope and 100 ohm resistors to test them. Basically, you tap into the trigger coils (two at once, in separate channels, is preferred, as you can compare to each other), with one pulse every 360 degrees. The higher the rev, the higher the voltage pulse.

 

 

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