Caravan AWD V6-201 3.3L (1991)
Ignition Coil: Description and Operation
The Direct Ignition System (DIS) uses a coil pack that actually contains 3 separate coils. Each coil fires 2 cylinders every power stroke. This firing
system is commonly referred to as the "waste spark method". It is called this because, while one cylinder fires during the compression stroke, its mating
cylinder is firing during its exhaust stroke.
Each coil is designed to step up primary voltage of 12V to 25,000-35,000V. It is composed of a primary winding, secondary winding and a core of soft
iron. The primary winding is made up of approximately 200 turns of heavy wire (approximately No. 18 gauge). The secondary winding is wound around
the soft iron core, and the primary wiring surrounds the secondary. The purpose of the core is to concentrate the magnetic field. It transforms the battery
voltage to the high secondary voltage (about 28 Kv.) every time it receives a signal.
The coil pack is powered by the ASD relay, and controlled by the engine controller. The ASD relay sends voltage to the positive side of each of the
three coils, and the engine controller is connected to and controls the negative side. The engine controller applies and removes the ground from the coils
according to signals it receives from various sensor inputs. When the engine controller applies the ground to the coil, secondary voltage is discharged to
the spark plugs. When the ground is removed from the coil circuit, secondary voltage is not allowed to flow to the spark plugs until the engine controller
re-applies the ground.
