Wrap-Up

Ready for Review

• The ignition system starts with an input from the engine to determine at what point a spark needs to occur.
• A primary circuit is what is controlled by the ignition module or breaker points.
• The moment that the primary circuit is turned off, the electric field collapses onto the secondary circuit.
• The secondary circuit is connected to the spark plugs by the HT wires.
• Having a good power source is necessary to maintain the full function of the ignition system.
• The trigger circuit turns the coil on and off, which is related to the position of the rotating assembly.
• The dwell of a coil is the amount of time that it is charging until the power is turned off.
• Coils are just small gauge wires that are wound in tight circles to create an electromagnet.
• HT leads are insulated to hold the high voltage that is transferred from the coil/distributor to the spark plug.
• Coil packs are used in a waste spark type of system.
• Coil-on-plug (COP) or coil-near-plug (CNP) ignition systems are used to enable control over each cylinder individually.
• Breaker-point ignition systems are low voltage and require regular maintenance.
• High-quality spark plugs are necessary to maintain the ignition system’s integrity.
• Copper spark plugs work well but wear fast.
• Platinum spark plugs have a longer life because of the harder metal used for the electrode.
• Iridium spark plugs are the longest-lasting spark plugs on the market currently.

Key Terms

after top dead center (ATDC)  A point after top dead center.

before top dead center (BTDC)  An event happening before the piston reaches its highest point in the cylinder.

coil-near-plug (CNP)  An ignition coil that is near the spark plug and has a connection with a spark plug wire to connect it to the spark plug.

coil-on-plug (COP)  An ignition coil that is mounted directly above the ignition coil. This type of ignition coil system has one coil for every cylinder.

coil pack  A group of two or more ignition coils housed in one assembly.

conductors  A material with low resistance for electron movement, used for current to flow in a circuit.

electromagnetism  Magnetism that is created by running voltage through a coil.

electromotive force  The pressure or push generated by any source of energy that causes electrons to flow in a conductor.

Faraday’s law  A law that states that the relative movement between a conductor and a magnetic field allows four ways by which voltage can be induced in a conductor.

inductance  The transfer (creation) of energy from the primary coil windings to the secondary windings. Ignition coils rely on inductance.

ionization  A phenomenon that occurs when the coil’s high-voltage discharge across the spark plug gap causes the electrons in the air-fuel mixture to split and form a conductive path for current to flow.

Lenz’s law  States that the induced current flows in the opposite direction from the initial change in current that produced the magnetic field.

magnetic field  The moving magnetic flux lines (field) induce a current in the secondary windings.

Oersted’s law  A constant electric current flow generates a magnetic field around the conductor.

polarity  The state of charge—positive or negative.

primary circuit  The low-voltage circuit that turns the coil on and off.

resistance  The opposition to current flow through a conductor.

secondary capacitance  A condition that occurs when all the secondary components are pre-charged with the release of high energy from the secondary coil windings just before the spark plug gap ionizes and the plug fires.

secondary circuit  The part of an ignition system that operates on higher voltage and delivers the necessary high voltage to the spark plug.

spark plug  A plated metal shell with a ceramic insulator, a resistor, and an electrode that extends through the center of the insulator, a side electrode, and an air gap.

transistor  A semiconductor device usually made with three layers of doped silicon material. Bipolar transistors can be constructed as PNP or NPN types. A transistor has a base, collector, and emitter. A small current at the base controls a larger current through the collector and emitter. The emitter is denoted by an arrow, which usually points toward the ground portion of the circuit.

triggering circuit  The triggering device produces the signal to the ICM or PCM for coil switching. This circuit uses the device to turn a coil on and off.

Review Questions

1. A coil’s primary winding charges to produce the spark for the spark plug, creating a magnetic field. Once it has been shut off, ___________.
   • it dissipates
   • it collapses onto the secondary windings and is sent to the spark plug
   • it turns the spark production on to the ignition coil
   • it is absorbed by the PCM
2. The heat range on a spark plug determines which one of the following aspects of the spark plug?
   • How the hot the cylinder gets with the plug installed.
   • How hot the spark gets when it is fired by the distributor.
   • How well the spark plug dispels heat.
   • How efficiently the spark plug ignites the air-fuel mixture.
3. To determine the wattage of the coil, which one of the following equations should be used?
   • E × I = W.
   • E ÷ I = W.
   • I ÷ W = E.
   • I × W = E.
4. Choose the correct statement.
   • Spark plugs are made to wear and require periodic replacement.
   • Any spark plug can be used in a vehicle because it merely finishes the ignition process.
   • The voltage that is produced by the ignition coil can overcome worn-out spark plugs.
   • Spark plug wires never require replacement, because they do not move.
5. The difference between a conventional spark plug and an iridium spark plug allow the iridium spark plug to do what?
   • It changes the firing order of the engine.
   • It produces more voltage.
   • It provides a longer service life than a conventional spark plug can.
   • It increases the power that is used to spark the spark plug.
6. Once the primary ignition system voltage has been transferred to the secondary ignition coil, what happens to the voltage?
   • It increases.
   • It decreases.
   • It stays the same.
   • It is determined by the ignition switch position.
7. Choose the correct statement.
   • Copper spark plugs outlast every other type of spark plug.
   • Coil dwell is the amount of time it takes to charge the ignition coil.
   • The distributor does not determine which cylinder receives the power from the coil.
   • Having a charging system or battery issue will not affect the ignition system.
8. On a coil pack or in distributorless ignition system (DIS), the coils are encased in what?
   • Gel.
   • Oil.
   • Resin/plastic.
   • Steel.
9. An EI system with a distributor triggers the ignition coil with what component?
   • The ignition switch.
   • The distributor.
   • The ignition control module (ICM).
   • The battery.
10. On a coil-on-plug (COP) ignition system, the powertrain control module (PCM) fires each individual coil based on sensor inputs from the engine. Which one of the following sensors is one of those inputs?
    • Mass airflow (MAF).
    • Oil pressure sender.
    • Transmission temperature.
    • Crankshaft (CKS) position.

ASE Technician A/Technician B–Style Questions

1. Technician A says spark plugs should be replaced only if customer wants them to be replaced. Technician B says that ignition coils are step-up transformers. Who is correct?
   • Technician A
   • Technician B
   • Both A and B
   • Neither A nor B
2. Technician A says COP means that the coil is on top of the spark plug. Technician B says EI systems eliminate moving parts to increase longevity. Who is correct?
   • Technician A
   • Technician B
   • Both A and B
   • Neither A nor B
3. Technician A says that ICMs in an EI system control when the coil is turned on and off. Technician B says that having a substandard battery will not affect the ignition system, because it uses low voltage. Who is correct?
   • Technician A
   • Technician B
   • Both A and B
   • Neither A nor B
4. Technician A says that a coil pack is used on a vehicle with a distributor. Technician B says that the heat range of a spark plug is how hot it sparks. Who is correct?
   • Technician A
   • Technician B
   • Both A and B
   • Neither A nor B
5. Technician A says the HT leads are able to transfer the voltage from the distributor to the spark plugs with little power loss. Technician B says that in a COP system, spark timing is controlled by the PCM. Who is correct?
   • Technician A
   • Technician B
   • Both A and B
   • Neither A nor B
6. Technician A says a conventional ignition coil has three coils inside of a single housing. Technician B says a conventional ignition coil has oil in the housing to cool the coils as they operate. Who is correct?
   • Technician A
   • Technician B
   • Both A and B
   • Neither A nor B
7. Technician A says that iridium spark plugs have a hard metal for the conductor within the spark plug, which leads to a short life of the spark plug. Technician B says the spark plug gap doesn’t matter for the operation of the vehicle. Who is correct?
   • Technician A
   • Technician B
   • Both A and B
   • Neither A nor B
8. Technician A says the ICM on an engine controls the operation of the distributor. Technician B says that dwell is adjustable on later-model vehicles so that the engine can be finely tuned. Who is correct?
   • Technician A
   • Technician B
   • Both A and B
   • Neither A nor B
9. Technician A says that the operation of the ignition switch should be verified to determine whether it is feeding the ICM/PCM 12 volts when diagnosing a no-start. Technician B says that coil operation is necessary to produce spark in the ignition system. Who is correct?
   • Technician A
   • Technician B
   • Both A and B
   • Neither A nor B
10. Technician A says a waste spark ignition system fires two opposite spark plugs with every event. Technician B says that COP ignition systems are not as precise as coil pack ignition systems. Who is correct?
    • Technician A
    • Technician B
    • Both A and B
    • Neither A nor B