Nissan Repair: missfire, haynes manual, noid light

Question
I am not getting any spark at the drivers side rear spark plug. I checked compression-ok- checked coil pack - ok- checked plug -ok- . There is power to the connector, and the ground is working. What can i check for ohms or voltage and where does the fire command come from? Could this be a ecu problem or some sensor? I have power at the center prong, ground at one and nothing at the third prong. When should it be live?

Answer
Kees,

Pull the plug and insert it in the coil and ground the side of the plug to the block and have someone turn over the engine.  It sounds like the plug is defective if you are not getting power at the cylinder you describe.  A noid light can be used to see if you are getting switching signal to the coil in question.  Also, I like to move coils and plugs to a different hole to see if the problem follows the coil and plug.  That way you know if it is the coil and plug or if there is something like a burnt valve in a particular cylinder.  A Haynes Manual has the procedure to test the coils and it gives you the values to measure.