coil spark test

[chuck hahn]

So im setting here thinking about a way to test a coil off of a bike. I was thinking run a ground wire off one mounting hole to the battery then touch the hot wire to battery positive and signal wire from the ignition to the battery negative. In theory when i take the trigger wire off the battey negative it should fire the spark plug. Does this sound like it will work to actually fire a plug off?

[pdqford]

No. It’s not that complicated.

Just run a jumper wire from a 12V battery positive post to the coil’s positive connector.

And run a jumper wire from the battery’s negative post to the coil’s negative connector.

Don’t leave it connected long as that will continuously charge up the coil’s primary circuit.

When you remove the negative wire the coil’s primary circuit collapses causing the coils secondary circuit to generate a high voltage spark from the coil’s high tension (sparkplug wire) port.

[chuck hahn]

Cool. i will give that a go

[pdqford]

After re-reading your post, you raise a good point, for which I am not sure.
Does the high voltage spark have to have a return path back to the coil in order to generate a spark?

[chuck hahn]

dont know but a ground from the coil mounting hole surely wont gurt anything is my thoughts

[Killer2600]

Does the high voltage spark have to have a return path back to the coil in order to generate a spark?

Yes, it does. Dual output coils will use the other HT lead as the return path so if you connect two plugs up and ground them together you’ll have a complete secondary circuit.

[pdqford]

Ah-ha. Thank You killer. Yes, the spark will jump from the center electrode to the side electrode on one plug and on the companion plug it will jump from the side electrode to the center electrode.