Ignition Systems Flashcards

What is the primary purpose of the ignition coil in a gasoline engine?

Answer: To step up battery voltage to fire spark plugs

The ignition coil transforms 12V battery voltage into the 20,000–45,000V needed to arc across the spark plug gap and ignite the air-fuel mixture.

Which type of ignition system eliminates the need for a distributor entirely?

Answer: Distributor-less ignition system (DIS)

A distributor-less ignition system (DIS) uses multiple ignition coils controlled directly by the PCM to fire cylinders without any mechanical distribution of spark.

In a distributor-based ignition system, what mechanism advances spark timing as engine RPM increases?

Answer: Centrifugal flyweight advance

The centrifugal advance mechanism uses flyweights inside the distributor that move outward at higher RPM, mechanically advancing ignition timing.

What is the typical voltage range produced by the secondary ignition circuit?

Answer: 20,000–45,000 volts

The secondary ignition circuit produces 20,000 to 45,000 volts — enough to ionize the air-fuel mixture and create a reliable spark under compression.

What instrument is used to read and set ignition timing on older distributor-equipped vehicles?

Answer: Timing light (stroboscope)

A timing light flashes in sync with cylinder #1 firing, freezing the timing mark on the harmonic balancer so the technician can read and adjust base timing.

What information does the crankshaft position sensor primarily provide to the ignition system?

Answer: Engine RPM and piston position

The crankshaft position sensor provides the PCM with precise crankshaft speed (RPM) and piston position data required to calculate accurate ignition timing.

What is the purpose of the spark plug gap?

Answer: To provide the correct arc distance for igniting the air-fuel mixture

The spark plug gap is the precise distance the high-voltage arc must jump; the correct gap ensures a strong spark that reliably ignites the compressed air-fuel mixture.