ASE Ignition Systems 1 — Questions and Answers
Question 1: What is the primary purpose of the ignition coil in a gasoline engine?
- To filter fuel impurities before combustion
- To step up battery voltage to fire spark plugs (Correct answer)
- To control valve timing mechanically
- To regulate fuel injector pulse width
Correct 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.
Question 2: Which type of ignition system eliminates the need for a distributor entirely?
- Breaker point ignition
- Electronic ignition with distributor
- Distributor-less ignition system (DIS) (Correct answer)
- Mechanical advance ignition
Correct 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.
Question 3: In a distributor-based ignition system, what mechanism advances spark timing as engine RPM increases?
- Vacuum advance diaphragm
- Centrifugal flyweight advance (Correct answer)
- EGR valve modulation
- Throttle position sensor feedback
Correct answer: Centrifugal flyweight advance
The centrifugal advance mechanism uses flyweights inside the distributor that move outward at higher RPM, mechanically advancing ignition timing.
Question 4: What is the typical voltage range produced by the secondary ignition circuit?
- 12–15 volts
- 100–500 volts
- 5,000–10,000 volts
- 20,000–45,000 volts (Correct answer)
Correct 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.
Question 5: What instrument is used to read and set ignition timing on older distributor-equipped vehicles?
- Digital multimeter
- Vacuum gauge
- Timing light (stroboscope) (Correct answer)
- Oscilloscope
Correct 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.
Question 6: What information does the crankshaft position sensor primarily provide to the ignition system?
- Engine coolant temperature
- Engine RPM and piston position (Correct answer)
- Exhaust oxygen content
- Fuel trim correction data
Correct 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.
Question 7: What is the purpose of the spark plug gap?
- To prevent fuel fouling of the electrode
- To create resistance for current regulation
- To provide the correct arc distance for igniting the air-fuel mixture (Correct answer)
- To cool the center electrode during combustion
Correct 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.
ASE Ignition Systems 1
What is the primary purpose of the ignition coil in a gasoline engine?