Secondary Ignition Troubleshooting

[Area 51%]

Dennis,


For testing the triggers, it's probably best to just attempt to use them as intended and see if they output 12v and drop to 0 whenever a magnet moves by. I did this on my workbench, but if you're careful it can probably be done on the airplane. I've never had a trigger failure so tend to be suspicious of the coils.

So there I was, all excited that the engine cranked over when I asked it to, and showed oil pressure almost immediately with the bottom plugs out. Time to test for spark. Magnatrons show a weak spark, but I didn't expect much from them at cranking speed. Nobody home on either secondary coil.

There is power to the coils and triggers. The grounds are intact. The measured voltage at the coils is the same as the battery. The coils get warm after a minute or two and there is a voltage drop when they are on, so I'm confident they are not the problem. When I test for power at the orange trigger wire (connected to the coil), I see maybe a volt or two max with nothing happening as the little magnet passes by the triggers. I removed one of the orange wires from it's coil and had the same test results.

Judges??

[gammaxy]

The voltage you are measuring at the orange wire sounds about right to me. The trigger is internally connecting the orange wire to ground through a semiconductor switch in order to allow current to flow through the coil. That the coils heat up is evidence that at least that part of the trigger is working. Very briefly, as the magnet passes, the voltage on the orange should be the same as the red wire because no current is flowing through it. If you're turning it slowly enough, you should notice a twitch of the needle on an analog multimeter.

When testing, keep in mind that the spark completes a circuit between the two high voltage terminals on the coil, so if you only have one lead connected or are missing one of the spark plugs, you probably won't see much. If you do, it's because electricity found an unintended way to complete the circuit.

To verify your testing method, you could remove the orange wire from the coil and find a way to switch that terminal to ground. When you disconnect it from ground, you should definitely get a spark at the plugs. If you do, then you can figure out if it's a problem with the triggers or the magnet.

[Area 51%]

How critical is the distance between the magnet and the trigger module? The geometry of the slots in the trigger is not user friendly for adjustment. Instead of parallel, they are at an angle to each other allowing only minimal movement.

On top of that, when our trigger/plate assembly finally showed up ( there were supply issues along with a recall at that time), the two triggers were nowhere close to being the same distance from the center of the plate; meaning the gaps between the magnet and the triggers were vastly different...with no way to adjust.

If the gap needs to be somewhere around .020 as somebody stated, then I have work to do to move the triggers inboard.

If it matters, there is a grey substance that oozed from the wire entry holes that looks like it may be some kind of epoxy. It came from the factory that way.

Thanks smart people.

[gammaxy]

Mine have the same ooze and work fine. I have a spare without any ooze so don't know if manufacturing has changed or if mine oozed after installation, but it doesn't seem to have caused a problem.

If they aren't centered very well as you describe, I'd expect that means one would be closer and one further away. The closer one should definitely fire. Another idea you might try is to remove the trigger module and see if you can trigger it manually with a magnet. I can easily trigger it by moving a small neodymium magnet up to the bump on the module.

[Area 51%]

At the very least, if the engine were running, I would expect the timing to be different between the two triggers because of the difference in gap. Not knowing squatt about electronics, maybe it doesn't matter?

Using a wire from the coil terminal to ground as a trigger got me sparks for about 15 seconds...nothing since.

If they aren't centered very well as you describe, I'd expect that means one would be closer and one further away. The closer one should definitely fire. Another idea you might try is to remove the trigger module and see if you can trigger it manually with a magnet. I can easily trigger it by moving a small neodymium magnet up to the bump on the module.

I'll try that next. Thanks.

This turd would be running by now if it had points like my Beetle.

[Area 51%]

It took a week to get to the bottom of it, but the problem has been at least partially identified as bad triggers. The test involves checking for continuity between the orange wire and the base of the trigger. There should be none. I have some.

Many thanks to Barry Hall for pulling his triggers out of stasis, and testing, so I had a baseline. (Barry Hall-hall effect sensors....hmmmmm)

The question now is weather that is the ONLY problem with my secondary ignition. I have no faith at all that the coils weren't manufactured by the same company that made the triggers. So I will have doubts about their integrity till either the new triggers cause the coils to vomit electrons, or I figure out how to test them.

P.S. There should be just under 2ohms if you test between the black and orange wires.