Ignition Coil Pack: Description and Operation

Ignition Coil Pack:

The coil pack contains three separate ignition coils which are controlled by the EDIS module through three coil leads. Signals from the module cause two spark plugs to fire simultaneously. One plug fires to ignite the air/fuel mixture in a cylinder on its compression stroke and the other fires on the mating cylinder which is on its exhaust stroke. Next time the coil is fired, the situation is reversed. Each following pair of plugs will fire according to engine firing order.

Plugs fired on the compression stroke use the majority of coil stored energy while those fired on the exhaust stroke use very little energy. Because spark plug pairs are connected in series, the firing voltage of one plug will be negative with respect to ground while the other will be positive.