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Difficulty: MediumIgnition System

Modern vehicles utilize electronic control units to precisely orchestrate spark generation at each cylinder. Arrange the operational phases of a coil-on-plug (COP) firing cycle in the correct chronological order from initial sensor input to spark delivery.

  1. 1The crankshaft and camshaft position sensors transmit reference pulses to the engine control module to determine piston location.
  2. 2The ignition driver completes the primary coil circuit, allowing current to flow and saturate the core with a magnetic field.
  3. 3The control module opens the primary circuit switch, causing the saturated magnetic field to rapidly collapse.
  4. 4High voltage is induced in the secondary winding, ionizing the air gap and discharging an electric arc across the spark plug electrodes.

Answer

The correct chronological sequence is: (1) Position sensor signal transmission to the engine control module, (2) Primary circuit dwell to build the magnetic field, (3) Primary circuit interruption causing magnetic field collapse, and (4) Secondary winding high-voltage induction and spark gap discharge.
An electronic ignition cycle begins when position sensors inform the engine computer of crankshaft angle and cylinder position. The computer activates the coil's primary circuit driver to establish a strong magnetic field (dwell). When ignition is commanded, the driver opens the primary circuit; the resulting instantaneous magnetic collapse cuts across thousands of secondary winding turns, stepping battery voltage up to tens of thousands of volts, which jumps the spark plug gap.

Step-by-Step Solution

1
Identify the initiating timing input
Crankshaft and camshaft position sensor pulses provide the engine control module with precise piston position data.
The computer cannot calculate dwell timing or advance without rotational reference signals.
2
Trace the energy storage phase in the ignition coil
Current flows through the primary winding during the dwell period, saturating the magnetic core.
Magnetic flux must be fully established in the primary winding before a secondary pulse can be generated.
3
Identify the switching trigger that releases stored energy
The primary circuit ground is opened, causing instantaneous collapse of the magnetic field.
Faraday's law of induction dictates that voltage magnitude depends directly on the speed of magnetic field collapse across the windings.
4
Trace the final delivery of stepped-up secondary voltage
The thousands of secondary turns produce 20,000 to 50,000 volts, ionizing the plug gap and jumping across the electrodes.
The extreme step-up ratio overcomes the high electrical resistance of dense, compressed cylinder gases to ignite the mixture.

Key Concept

Electronic Ignition Primary-to-Secondary Transformation and Timing Sequence
Estimated Time:1m 0s
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Topics

Ignition System

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