Mx5 nc spark mystery

[earthling]

Hi can anyone help please? Mx5 nc. Changed engine all okay apart from cylinder 4 not sparking. Have done all usual swap arounds, changed connector and pigtail. No difference …. Put coil pack on plug external … ofcourse no spark as rocker cover is plastic . Connected jump lead to plug with intention of earthling when engine running . Started up engine , plug was sparking even though I had not earthed jumper lead …. Removed jumper lead end from plug body …. Spark stopped . Sorry if that’s confusing.

Any ideas what’s going on ?

Thanks in advance

Adam

[GreenV8S]

earthling said:

Mx5 nc. Changed engine all okay

You might want to expand on that a bit.

Also worth expanding exactly what you tried swapping. If the problem only affects one plug you can usually track the problem down by swapping components between good and bad plugs to see which components the problem moves with.

From your description, all the jumper cable is doing is applying mechanical pressure to the connector. However, if it's sparking the spark must be going somewhere ie there must be an electrical path from the body of the plug to the other side of the coil.