Dumb coil question

[hobieboy]

In a waste spark set up, each coil has 2 outputs that drives 2 "opposing" cylinders (e.g. 1-4, 2-5, 3-6 in my case for a 6 cylinder).

If I disconnect one of the spark plug wires, say from cylinder 4. Will it also cause 1 to NOT fire?

I read somewhere that the secondary side needs to complete its circuit for the plug to fire. Does that mean the circuit needs both plugs to be grounded?

[PSIG]

If I disconnect one of the spark plug wires, say from cylinder 4. Will it also cause 1 to NOT fire?
I read somewhere that the secondary side needs to complete its circuit for the plug to fire. Does that mean the circuit needs both plugs to be grounded?

For most waste-spark type dual terminal coils, that is technically true. However, lots of voltage tends to find it's way around such obstacles and will arc in, around, and through some interesting paths to complete it's circuit. If it manages to do this by arcing through a weak point in the internal insulaton of the coil you can invisibly damage or destroy the coil and, although it will then fire the remaining plug in doing so, that gets very expensive.

This is one reason service manuals strongly caution the plug leads NOT be pulled while running as just one spark attempt while the wire is ungrounded can cause the arc damage. The suggestion is to always ground the wires or plugs with the ignition off to allow the system to complete the circuit in a normal fashion once energized.

So the short answer to your question is definitely an absolute maybe.

David

[hobieboy]

Well - that may explain why I can start the car but one of the coil pack seems to be not sparking consistently. That may be the weak coil pack.

So, I can try to hook all cylinders up to a single coil pack & if I start getting consistent spark, that may explain my issue.

[hobieboy]

Just a follow up - I connected all 6 cylinders to a single coil and leave the 2nd coil out of the picture completely. And she fired up right away. So I think that was the culprit of my starting problem for the longest time - one set of output on each coil was NOT connected to anything causing unstable ignition.

I removed the 2nd coil and tested its resistance & inductance. All within spec. Hope I didn't damage it. Will try to use this instead of "the other" coil tonight & see if I can still reliably start & run the car.