The ignition coil actually consists of two separate windings that supply spark to two cylinders each (one to cylinders 1 and 4, the other to cylinders 2 and 3). The ignition pulse is sent to two spark plugs at once for each engine cycle: one on the compression stroke, one on the exhaust stroke. The ignition spark on the exhaust stroke has no effect on engine operation and is therefore wasted. The ECU uses inputs from various sensors to calculate the required ignition timing and the energy storage time in the ignition coil.
Precautions
In an electronic ignition system, the ignition voltage is approximately 37 kV. Under unfavorable circumstances (high humidity in the engine compartment), voltage peaks can break through the insulation and cause shock when touched. To avoid injury and damage to the ignition system, the following should be taken into account when working on the system:
- do not touch or disconnect the ignition wire with the engine running or when turning the engine crankshaft with the starter;
- disconnect the ignition system wires. connect and disconnect any measuring devices only when the ignition is off;
- the ignition coil must not be replaced with another design. Under no circumstances should an ignition coil intended for a system with a breaker be installed;
- when heated to more than 80° (when painting a car), the engine must not be started immediately after heating;
- wash the engine only when the engine is not running;
- when carrying out electric welding work, it is necessary to disconnect the battery;
- persons with a pacemaker are prohibited from working on the ignition system.
[The text was obtained in its entirety from the specified website: fordbook]