How do the three types of vehicle ignition systems differ from each other?
I'm going to commit the unpardonable sin and "assume" that the three types of ignition systems being referred to are the points, coil pack, and coil-on-plug. There are actually four types of vehicle ignition systems.
Points-type ignition systems that were used on vehicles up through the early 1980’s are mechanical and can be adjusted. This system used a single ignition coil to spark all of the cylinders. The typical ignition tune-up required the replacement of the contact points, condenser, spark plugs, distributor cap, rotor, and possibly the spark plug wires. The points had to be adjusted for proper air gap when open to allow the ignition system to work as designed.
The first type of electronic ignition still used a distributor cap, rotor, and spark plug wires. This system replaced the contact points and condenser with a trigger wheel, called a reluctor, and an electronic pickup. A small ignition control module was used to control the spark timing.
Coil pack ignition systems are fully electronic and, as such, have no distributor, rotor, contact points, or condenser. This system uses a crankshaft position sensor and a camshaft position sensor. Coil pack ignitions have either two or three ignition coils mounted together in a single assembly. Spark plug wires are attached to the coil towers and are routed to their respective spark plug.
Coil-on-plug ignition systems are also fully electronic and, likewise, use a crankshaft position sensor and a camshaft position sensor. Coil-on-plug systems use a single ignition coil for each spark plug. This system does not use spark plug wires because the ignition coils sit directly on top of its respective spark plug.
Coil-on-plug ignition systems have a modified cousin. On vehicles that have two spark plugs per cylinder, you will have an ignition coil sitting on top of one plug while a second coil is mounted nearby and is connected to its spark plug with a short plug wire.
Whatever type of ignition system your car has, a professional technician can help you out with almost any spark related issue. They can also replace your spark plugs if necessary and at your own convenience.
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