W 250 Pickup V8-5.9L VIN Z (1991)
Ignition Coil: Description and Operation
The Ignition 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 ignition coil is powered by the ASD relay, and controlled by the engine controller. The ASD relay sends voltage to the positive side of the coil, and
the engine controller is connected to and controls the negative side. The engine controller applies and removes the ground from the coil 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 via the distributor. 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.
