Ignition Coil: Description and Operation

Coil Pack

2.5L Contour/Mystique, 2.5L Cougar, 3.0L Taurus/Sable, Windstar, 3.8L, and 3.0L Ranger, 4.2L E/F-Series, 3.8L Mustang, Series (Vertical Connector Six Tower Coil Pack):

Coil Pack

Fig. 53

4.0L Ranger, 4.0L Explorer and 4.0L SOHC Explorer/Mountaineer (Horizontal Connector Six Tower Coil Pack):

Fig. 54

Four - Tower Coil Packs:

Fig. 55

Coil packs come in four tower, six-tower horizontal connector and Six tower horizontal models. Two adjacent coil towers share a common coil and are called a matched pair. For six-tower coil pack (six cylinder) applications the matched pairs are 1 and 5, 2 and 6, and 3 and 4 (Figure 53)and (Figure 54).For duel four-tower coil pack (eight cylinder) applications the matched pairs are 1 and 6, 3 and 5, 4 and 7, and 2 and 8 (Figure 55) For four-tower coil pack (four cylinder) applications the matched pairs are 1 and 4, and 2 and 3 (Figure 55) and.

When the coil is fired by the PCM, spark is delivered through the matched pair towers to their respective spark plugs. The spark plugs are fired simultaneously and are paired so that as one fires on the compression stroke, the other spark plug fires on the exhaust stroke. The next time the coil is fired the situation is reversed. The next pair of spark plugs fire according to the engine firing order.

Two ignition coil packs are used for the 2.5 twin-plug engine. The two ignition coil packs are triggered and timed by the powertrain control module. Each coil pack contains two separate ignition coils for a total of four ignition coils. Each ignition coil fires two spark plugs simultaneously, one spark plug on the compression stroke and one on the exhaust stroke. The spark plug fired on the exhaust stroke uses very little of the ignition coil's stored energy. The majority of the energy is used by the spark plug on the compression stroke. Since these two spark plugs are connected in series, the firing voltage of one spark plug will be negative with respect to ground, while the other will be positive with respect to ground. Refer to Powertrain Management for additional information on spark plug polarity.