Examkin

Ignition System

25 questions

All types25Multiple choice12Matching7Ordering6
Question 1Question →

In an electronic ignition system, several sequential events must take place to ignite the compressed air-fuel mixture in a cylinder. Arrange the following operational steps in chronological order, from initial engine position detection to cylinder combustion. What is the correct sequence of these events?

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological sequence begins with the crankshaft position sensor transmitting a timing signal, followed by the engine control module interrupting the primary circuit, which causes the coil magnetic field to collapse and induce high secondary voltage, and finishes with the high-voltage pulse jumping the spark plug gap.
The correct sequence follows the fundamental flow of modern electronic ignition: sensing engine position (crankshaft sensor), command switching (module cuts primary current), voltage step-up (collapsing magnetic field induces secondary high voltage), and spark discharge (arc jumps the spark plug electrode gap).

Step-by-Step Solution

1
Identify the initiating trigger event in the electronic ignition system.
The crankshaft position sensor monitors engine rotation and provides the timing baseline signal to the control unit.
Electronic systems cannot determine when to fire without initial position input from the engine rotation sensor.
2
Determine the control response to the trigger signal.
The engine control module opens the primary ignition circuit, interrupting low-voltage battery current.
Breaking the primary circuit is the mechanical or solid-state action required to collapse the coil's magnetic field.
3
Trace the magnetic induction response inside the ignition coil.
The collapsing magnetic field cuts through thousands of fine secondary winding turns, stepping up the potential into tens of thousands of volts.
Mutual induction converts low-voltage primary switching into the high-voltage spike needed for ignition.
4
Identify the delivery and combustion stage.
The high-voltage surge reaches the spark plug and arcs across the gap, igniting the compressed charge.
The electrical arc at the spark plug electrodes is the final operational objective of the ignition circuit.

Key Concept

Electronic Ignition Triggering and High-Voltage Induction Sequence
Estimated Time:45s
Question 2Question →

An automotive technician is troubleshooting an engine that cranks normally but will not start due to a lack of spark at the cylinders. Which of the following functions must the ignition system perform to produce the necessary spark across the spark plug gaps?

Show answer & explanation

Answer: Transform low battery voltage into high secondary voltage through electromagnetic induction

Answer

Transform low battery voltage into high secondary voltage through electromagnetic induction
The correct response accurately states that the ignition system uses electromagnetic induction in the ignition coil to transform low primary battery voltage (12 volts) into high secondary voltage (typically 20,000 to 50,000 volts). This high voltage is essential to ionize the gap between the spark plug electrodes under high cylinder pressure.

Step-by-Step Solution

1
Identify the electrical potential needed to bridge a spark plug gap under cylinder compression
Recognize that ionizing the compressed air-fuel gap requires between 20,000 and 50,000 volts, far exceeding standard 12V automotive battery voltage.
Air and atomized fuel under high pressure act as electrical insulators that require high dielectric breakdown voltage.
2
Determine the operating principle of the ignition coil
The ignition coil functions as a step-up transformer, utilizing electromagnetic mutual induction between primary and secondary windings when primary current is interrupted.
Rapid collapse of the primary magnetic field induces high voltage in the secondary winding with many more turns of wire.
3
Match the core function to the correct system requirement
The primary requirement of the ignition system is transforming 12V battery power into high-voltage secondary pulses delivered at the proper timing.
Without this voltage step-up, no spark can jump the electrode gap to initiate combustion.

Key Concept

Ignition Coil Voltage Step-Up via Electromagnetic Induction
Estimated Time:1m 0s
Question 3Question →

Match each automotive ignition system component with its primary operational function in controlling or delivering the spark.

Click a left item, then click its matching right item

Items

Ignition Control Module (ICM) switching transistor
Ignition coil step-up windings
Spark plug ceramic insulator and internal resistor
Centrifugal (mechanical) advance mechanism

Matches

Show answer & explanation

Answer

The Ignition Control Module switching transistor matches with rapidly opening and closing the primary circuit ground; the ignition coil step-up windings match with transforming low battery voltage into high-voltage pulses via mutual electromagnetic induction; the spark plug ceramic insulator and internal resistor match with preventing high-voltage flashover while suppressing radio frequency interference; and the centrifugal advance mechanism matches with shifting spark timing progressively earlier as engine speed increases.
Each pair correctly matches an essential ignition sub-function: primary switching via the control module transistor, electromagnetic step-up via the coil transformer windings, dielectric insulation and noise suppression via the spark plug ceramic and resistor, and RPM-dependent timing advance via the centrifugal flyweights.

Step-by-Step Solution

1
Analyze the primary circuit control component.
Identify that the Ignition Control Module (ICM) switching transistor controls the ground path of the primary winding, interrupting current to trigger magnetic collapse.
Primary switching is essential to generate inductive kickback and high secondary voltage.
2
Analyze the voltage transformation mechanism.
Identify that the primary and secondary windings in the ignition coil act as a transformer stepping up 12 V12\text{ V} into 20000 to 50000 V20{}000\text{ to }50{}000\text{ V}.
A high voltage is required to ionize the air-fuel gap across the spark plug electrodes.
3
Analyze spark plug insulation and radio suppression properties.
Identify that the spark plug ceramic body isolates extreme secondary voltage from the engine block, while the built-in resistive core prevents electrical noise across vehicle electronics.
Without proper insulation and resistance, misfires and radio frequency interference occur.
4
Analyze the engine speed timing adjustment mechanism.
Identify that centrifugal advance mechanisms use rotating weights to advance ignition timing before top dead center (BTDC) at elevated RPM.
Higher engine speeds leave less time per power stroke, requiring the fuel mixture to be ignited earlier.

Key Concept

Operational roles and electromagnetic principles of automotive ignition system components
Estimated Time:1m 30s
Question 4Question →

During a no-start diagnosis on an engine equipped with an electronic ignition system, a technician determines that battery voltage is present at the ignition coil positive terminal while cranking. However, when a test light is connected between the coil negative terminal and engine ground, the light glows steadily and fails to pulse as the engine turns over. Which of the following is the most likely cause of this no-spark condition?

Show answer & explanation

Answer: A failed ignition module or switching circuit that is unable to rapidly open and close the primary ground path

Answer

A failed ignition module or switching circuit that is unable to rapidly open and close the primary ground path
For an ignition coil to step up low battery voltage to the high voltage required to bridge the spark plug gap, current flowing through the primary winding must be repeatedly interrupted. When the ignition control module or electronic switching transistor opens the ground circuit, the magnetic field built up in the primary winding instantly collapses across the secondary winding, inducing high voltage. A test light that glows constantly without pulsing indicates that the module or switching circuit is not interrupting the ground path.

Step-by-Step Solution

1
Analyze the primary circuit power supply status.
Battery voltage is confirmed at the ignition coil positive terminal, proving the ignition switch and primary feed circuits are functioning properly.
Establishing that power reaches the coil isolates the fault to the coil itself, the secondary circuit, or the primary switching/ground path.
2
Interpret the test light behavior on the ignition coil negative terminal.
The test light remains constantly lit without pulsing or flashing during engine rotation.
The ignition control module (or switching transistor) must repeatedly ground and open the coil negative terminal to charge and collapse the primary magnetic field.
3
Determine the operational effect of a continuous, non-switching ground circuit.
Without rapid interruption of primary current, mutual electromagnetic induction cannot occur across the secondary winding.
High secondary voltage (20,000–50,000+ volts) is generated only when the primary magnetic field collapses rapidly across the fine secondary windings.

Key Concept

Ignition Coil Primary Circuit Switching and Electromagnetic Induction

Alternative Method

Connecting an automotive digital oscilloscope to the ignition coil negative terminal will display a flat 12-volt baseline rather than the expected switching waveform and 300V to 400V primary flyback spike, confirming the absence of ground switching.
Estimated Time:1m 30s
Question 5Question →

An automotive technician connects an oscilloscope to an inductive ignition coil and observes that the high-voltage firing spike occurs at the precise moment primary circuit current is interrupted by the switching module. Which of the following electrical processes causes the ignition coil to generate this high-voltage output needed to bridge the spark plug gap?

Show answer & explanation

Answer: The rapid collapse of the magnetic field in the primary winding cuts across the secondary winding, inducing a high-voltage surge.

Answer

The rapid collapse of the magnetic field in the primary winding cuts across the secondary winding, inducing a high-voltage surge.
An automotive ignition coil functions as a step-up pulse transformer. When the ignition module opens the primary circuit, current flow stops immediately. This causes the magnetic field created by the primary winding to collapse abruptly across the secondary winding. Because the secondary winding contains far more turns of finer wire than the primary winding, this rapid collapse induces a high-voltage spike (20,000 to 50,000+ volts) capable of arcing across the spark plug gap.

Step-by-Step Solution

1
Analyze primary circuit operation during dwell time.
Low-voltage current (12V) flows through the heavy primary winding turns, building a strong electromagnetic field around the soft iron core.
Current through an inductor stores energy in the form of a magnetic field.
2
Evaluate the switching event when the primary circuit is opened.
The primary circuit ground is interrupted, causing current flow to cease and the magnetic field to collapse almost instantaneously.
Removing current removes the magnetic field support, initiating rapid field decay.
3
Apply Faraday's law of mutual induction across the step-up windings.
The rapidly decaying magnetic field lines cut across the secondary winding's high number of turns, generating 20,000 to 50,000 volts.
Induced voltage is proportional to the rate of magnetic flux change and the ratio of secondary-to-primary turns.

Key Concept

Mutual electromagnetic induction and magnetic field collapse in step-up ignition coils
Estimated Time:1m 30s
Question 6Question →

Arrange the following events in the exact sequence they occur during the operation of a conventional electronic distributor ignition system, from the initial trigger signal to the final spark delivery.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is: trigger signal generation, primary ground interruption, primary magnetic field collapse, secondary high-voltage induction, and spark gap ionization.
The ignition sequence relies on electromagnetic principles. It starts with a timing signal (pickup stator), which tells the control module to break the primary circuit's ground. This sudden loss of current causes the primary magnetic field to collapse. As this field collapses, it cuts across the secondary winding, inducing a massive voltage spike through mutual induction. This high voltage then travels to the spark plug, overcoming gap resistance to create a spark.

Step-by-Step Solution

1
Identify the initial triggering event.
The reluctor wheel aligns with the magnetic pickup, generating an AC voltage signal.
The ignition sequence always begins with a sensor detecting the engine's rotational position to determine timing.
2
Determine the action taken by the ignition control module.
The ICM interrupts the ground path for the ignition coil's primary winding.
The module uses the AC signal to open the primary circuit, stopping current flow through the primary winding.
3
Analyze the immediate effect on the primary coil.
The magnetic field surrounding the primary winding rapidly collapses.
Without current flow to sustain it, the magnetic field built up around the primary winding collapses inward.
4
Identify the consequence of the collapsing magnetic field.
A high-voltage surge is induced in the secondary winding via mutual induction.
The collapsing magnetic lines of force cut across the thousands of turns in the secondary winding, stepping up the voltage.
5
Determine the final destination of the high voltage.
The high-voltage surge overcomes the resistance of the spark plug gap, ionizing the mixture.
The induced voltage travels through the secondary circuit to jump the plug gap, creating the required spark.

Key Concept

Ignition circuit sequence of operation and electromagnetic induction
Question 7Question →

Place the operational stages of automotive spark generation in chronological order, starting from the low-voltage circuit supply to the final ignition event.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence begins with primary winding energization to build a magnetic field, followed by current interruption to collapse the field, mutual induction of high voltage in the secondary winding, and finally the spark plug electrode discharge.
Automotive ignition operation relies on electromagnetic induction. First, battery current flows through the primary winding to store magnetic energy. Next, the primary circuit is broken by the control module, causing the magnetic field to collapse instantly across the secondary winding. This collapse induces a high-voltage pulse of 20,000–50,000 volts, which travels to the spark plug and jumps the gap to initiate combustion.

Step-by-Step Solution

1
Identify the initial power supply and field buildup stage.
Low-voltage current flows from the battery through the primary coil winding, creating an electromagnetic field.
An electromagnetic field must be established before high voltage can be generated.
2
Identify the switching mechanism that triggers induction.
The switching transistor or ignition control module abruptly turns off primary current.
Induction requires a changing magnetic field; cutting off current creates an instantaneous collapse.
3
Identify the voltage transformation stage.
The rapidly collapsing magnetic field induces a high-voltage surge in the secondary coil winding.
The high ratio of secondary-to-primary wire turns transforms 12 volts into tens of thousands of volts.
4
Identify the final delivery to the combustion chamber.
The high voltage reaches the spark plug and arcs across the air gap to ignite the fuel mixture.
The discharge of the secondary voltage creates the thermal spark needed for combustion.

Key Concept

Electromagnetic induction in ignition coils requires establishing a primary magnetic field and rapidly collapsing it to induce high secondary voltage.
Estimated Time:45s
Question 8Question →

Which component in an automotive ignition system is responsible for converting the vehicle's low 12-volt battery supply into the tens of thousands of volts needed to create an electric spark?

Show answer & explanation

Answer: Ignition coil

Answer

Ignition coil
The ignition coil serves as a step-up pulse transformer in the ignition circuit. It receives standard 12-volt direct current from the vehicle electrical system and, through electromagnetic induction caused by the rapid collapse of its primary magnetic field, steps that voltage up to the 20,000 to 50,000+ volts required to jump the spark plug gap and ignite the compressed air-fuel mixture.

Step-by-Step Solution

1
Identify the high-voltage requirement of an internal combustion engine's ignition system.
Standard automotive batteries provide approximately 12 volts, but creating an electrical arc across the spark plug gap requires 20,000 to 50,000 volts.
Air and compressed air-fuel mixtures have high electrical resistance and require high secondary voltage for ionization.
2
Identify the component designed to perform this step-up voltage transformation.
The ignition coil uses primary and secondary windings around an iron core to step up low direct current voltage via electromagnetic induction.
When primary current flow is interrupted, the rapid collapse of its magnetic field induces high voltage in the secondary winding.

Key Concept

Ignition coil step-up transformation
Estimated Time:45s
Question 9Question →

A standard automotive ignition system uses dedicated electrical components to deliver a timed electrical spark to the combustion chamber. Which primary operational role corresponds to each ignition system component listed below?

Click a left item, then click its matching right item

Items

Ignition switch
Ignition coil
Crankshaft position sensor
Spark plug

Matches

Show answer & explanation

Answer

The ignition switch connects primary battery power, the ignition coil steps up battery voltage into high secondary voltage, the crankshaft position sensor delivers precise timing signals, and the spark plug discharges the electric arc inside the combustion chamber.
Each component performs a distinct function in the sequence of spark creation: the ignition switch allows battery current into the primary circuit, the crankshaft position sensor sends timing data, the ignition coil steps up the voltage, and the spark plug discharges the high-voltage arc inside the combustion chamber.

Step-by-Step Solution

1
Identify the role of the primary power control device
The ignition switch controls low-voltage circuit connectivity from the battery.
Before high voltage can be generated, electrical current must be enabled to enter the primary circuit.
2
Identify the role of the voltage step-up transformer
The ignition coil transforms 12V primary current into high-voltage secondary output.
Battery voltage alone is insufficient to ionize air and jump the spark plug gap.
3
Identify the timing input sensor
The crankshaft position sensor detects piston position and engine speed.
Precise timing is necessary so ignition occurs before top dead center on the compression stroke.
4
Identify the final spark delivery component
The spark plug forces high-voltage current across its gap inside the cylinder.
The thermal energy of the spark initiates combustion of the compressed air-fuel charge.

Key Concept

Function and signal flow of core automotive ignition system components
Estimated Time:45s
Question 10Question →

During a routine engine tune-up, a technician uses a feeler gauge to measure and adjust the clearance between the center electrode and the ground electrode of each spark plug. What is the primary purpose of setting this specific spark plug gap?

Show answer & explanation

Answer: To ensure an electrical arc of sufficient energy forms to properly ignite the compressed air-fuel mixture

Answer

Setting the proper spark plug gap ensures an electrical arc of sufficient energy forms to properly ignite the compressed air-fuel mixture.
Maintaining the specified spark plug gap ensures that the secondary ignition voltage creates an electrical arc with sufficient energy to ignite the air-fuel mixture cleanly without causing ignition coil overload or spark blowout under cylinder compression.

Step-by-Step Solution

1
Identify the primary function of the spark plug in the ignition system.
The spark plug provides the physical air gap across which high secondary voltage arcs to initiate combustion.
The ignition system must reliably ignite the air-fuel mixture near the end of the compression stroke.
2
Analyze how electrode spacing influences spark formation and combustion.
A correctly gapped plug balances the voltage required to jump the gap with the arc duration needed for clean combustion.
A gap that is too wide can cause ignition misfires under cylinder compression, while a gap that is too narrow creates a weak spark that causes incomplete combustion.

Key Concept

Spark Plug Electrode Gap and Ignition Discharge
Estimated Time:45s
Question 11Question →

Modern gasoline engines rely on a dedicated ignition system to ignite the compressed air-fuel mixture inside each cylinder. What is the primary function of the ignition coil in this system?

Show answer & explanation

Answer: Transform low battery voltage into the high voltage needed to create a spark at the spark plug

Answer

Transform low battery voltage into the high voltage needed to create a spark at the spark plug
The correct answer identifies that the primary role of an ignition coil is to act as a step-up transformer, taking the 12-volt direct current from the vehicle's electrical system and multiplying it into the 20,000 to 50,000 volts required to ionize the air gap and create a reliable ignition arc at the spark plug.

Step-by-Step Solution

1
Identify the electrical requirements for creating a spark in an internal combustion engine
An automotive battery provides only 12 volts DC, but jumping the pressurized gap of a spark plug requires between 20,000 and 50,000 volts.
Electrical resistance across a spark plug gap under compression requires thousands of volts to ionize the gap and produce an electric arc.
2
Determine which ignition component performs the voltage step-up function
The ignition coil uses electromagnetic induction between primary and secondary windings to transform 12V into high-voltage pulses.
The ignition coil serves as a step-up transformer specifically designed to provide the necessary firing voltage.

Key Concept

The ignition coil acts as an electromagnetic step-up transformer to convert low primary circuit voltage into high secondary voltage for spark ignition.
Estimated Time:45s
Question 12Question →

In a traditional automotive ignition system, which component rotates inside the distributor cap to deliver high-voltage electricity to each spark plug in the correct firing order?

Show answer & explanation

Answer: Distributor rotor

Answer

Distributor rotor
In a conventional distributor-type ignition system, the distributor rotor is turned by the engine's camshaft. As it spins within the distributor cap, it receives high-voltage current from the central ignition coil lead and sweeps past individual contact points, distributing spark to the appropriate spark plug in accordance with the engine firing order.

Step-by-Step Solution

1
Identify the primary function described in the scenario
The component must physically rotate within the distributor cap to distribute secondary high voltage to spark plugs in a timed sequence.
Conventional distributor systems use a mechanical switching device timed to the camshaft to route spark energy to each cylinder.
2
Match the function to the correct automotive component
The distributor rotor sits beneath the distributor cap on the distributor shaft and sweeps across terminal contacts leading to each spark plug wire.
The rotor serves as the rotating bridge that channels coil voltage to the respective cylinder.

Key Concept

High-voltage spark distribution in distributor-based ignition systems
Estimated Time:45s
Question 13Question →

An internal combustion engine relies on several dedicated components in the ignition system to create and deliver spark. Match each ignition component to its primary operational role.

Click a left item, then click its matching right item

Items

Ignition Coil
Spark Plug
Ignition Control Module
Crankshaft Position Sensor

Matches

Show answer & explanation

Answer

Ignition Coil matches with stepping up low battery voltage to high voltage; Spark Plug matches with discharging current across an electrode gap; Ignition Control Module matches with switching primary circuit ground; Crankshaft Position Sensor matches with monitoring rotational position for timing.
Each item accurately pairs the functional component of an automotive ignition circuit with its direct role: the coil steps up voltage, the spark plug produces the ignition arc, the module switches the primary ground to trigger induction, and the crankshaft sensor measures engine rotation for precise ignition timing.

Step-by-Step Solution

1
Identify the high-voltage generator in the circuit
The ignition coil converts low DC battery voltage to high voltage through magnetic induction.
Air-fuel mixtures require tens of thousands of volts to ionize and bridge the plug gap.
2
Identify the combustion chamber firing device
The spark plug provides the physical gap where electrical arcing occurs.
The combustion event begins directly at the spark plug electrodes.
3
Identify the switching and triggering elements
The ignition control module handles primary circuit switching, while the crankshaft position sensor provides the timing reference signal.
Proper ignition synchronization requires both position sensing and solid-state primary circuit switching.

Key Concept

Ignition system core component identification and functional mapping
Estimated Time:50s
Question 14Question →

As an internal combustion engine accelerates to higher operating speeds (RPM), what adjustment must the ignition system make to spark timing to ensure maximum combustion pressure develops at the optimal point in the power stroke?

Show answer & explanation

Answer: Advance the spark timing so ignition occurs earlier before top dead center (TDC)

Answer

Advance the spark timing so ignition occurs earlier before top dead center (TDC)
Because the air-fuel mixture requires a finite and relatively constant duration to burn completely, firing the spark earlier before top dead center (advancing timing) at higher engine speeds ensures that peak cylinder pressure is reached just as the piston begins descending on the power stroke.

Step-by-Step Solution

1
Analyze the relationship between engine rotational speed and fuel combustion duration
As engine RPM increases, the piston completes its strokes in less time, while the air-fuel charge still requires approximately 2 to 3 milliseconds to reach peak combustion pressure.
Understanding that mechanical piston velocity changes with RPM while chemical flame propagation remains relatively constant is essential to spark timing.
2
Determine the necessary ignition timing correction
The ignition system must fire the spark plug earlier in the compression stroke (more degrees before top dead center, or advanced) so peak combustion pressure aligns with the start of the power stroke.
Advancing spark timing maintains optimal thermal efficiency and engine torque across varying RPM ranges.

Key Concept

Ignition timing advance compensates for increased piston speed at higher RPM by triggering the spark earlier before top dead center.
Estimated Time:1m 0s
Question 15Question →

An automotive ignition system requires several specialized electronic and mechanical components to control, trigger, and deliver electrical energy to the cylinders. Match each ignition system component with its primary operational function.

Click a left item, then click its matching right item

Items

Crankshaft Position Sensor
Ignition Control Module
Ignition Condenser (Capacitor)
Spark Plug Ceramic Insulator

Matches

Show answer & explanation

Answer

Crankshaft Position Sensor matches with monitoring rotational speed and piston position; Ignition Control Module matches with switching primary coil circuit current; Ignition Condenser matches with absorbing voltage surges across opening points; Spark Plug Ceramic Insulator matches with preventing voltage arcing to ground while conducting heat.
Each component serves a dedicated role in the generation, timing, delivery, and protection of the ignition circuit. The Crankshaft Position Sensor delivers timing data; the Ignition Control Module switches the primary coil ground; the Condenser buffers inductive back-EMF at contact points; and the Ceramic Insulator prevents spark short-circuits while regulating plug operating temperature.

Step-by-Step Solution

1
Identify the timing sensor component
The Crankshaft Position Sensor detects engine speed and Top Dead Center (TDC) reference points for ignition timing.
The engine computer requires precise rotational positioning data to command the spark.
2
Identify the switching device for primary voltage
The Ignition Control Module handles the rapid solid-state switching of primary current.
Interrupting primary current causes magnetic field collapse across the secondary coil windings.
3
Identify the electrical surge absorption component
The Ignition Condenser temporarily stores current as breaker points separate.
Without a condenser, electrical energy would arc across the contact points, burning them rapidly.
4
Identify the thermal and dielectric isolation component
The Spark Plug Ceramic Insulator isolates the high-voltage center electrode and dissipates thermal energy to the cylinder head.
Dielectric ceramic prevents current flashover and regulates plug heat range.

Key Concept

Roles and operations of primary switching, timing sensing, surge protection, and electrical insulation components in automotive ignition systems.
Estimated Time:1m 0s
Question 16Question →

A technician is diagnosing an engine no-start condition on a vehicle equipped with an electronic ignition system. Testing reveals that current is continuously flowing through the primary coil winding because the ignition control module fails to open or switch the circuit. What is the direct consequence of this failure on the ignition system?

Show answer & explanation

Answer: The primary magnetic field cannot rapidly collapse, preventing the induction of high secondary voltage needed to fire the spark plugs.

Answer

The primary magnetic field cannot rapidly collapse, preventing the induction of high secondary voltage needed to fire the spark plugs.
In an automotive ignition system, high voltage (typically 20,000 to 50,000 volts) is produced through mutual induction. Low-voltage battery current flows through the primary winding to build a strong magnetic field. When the ignition control module interrupts this primary current, the magnetic field collapses abruptly across the secondary winding, inducing the high voltage required to jump the spark plug gap. If the primary circuit is never opened, the magnetic field remains stationary, and no spark can be generated.

Step-by-Step Solution

1
Identify the operating principle of an automotive ignition coil.
An ignition coil acts as a step-up transformer that stores energy in a magnetic field created by low-voltage current in the primary winding.
Understanding transformer action is necessary to determine what triggers high-voltage generation.
2
Analyze the effect of interrupting primary circuit current.
When the ignition control module or switching transistor turns off (opens the circuit), the primary current drops to zero instantly, causing the magnetic field to collapse rapidly across the secondary winding.
Electromagnetic induction requires a rapid change in magnetic flux to induce high voltage (thousands of volts) across the thousands of secondary wire turns.
3
Determine the outcome if the primary circuit fails to open.
If current remains constant and does not collapse, no voltage is induced in the secondary winding, resulting in no spark at the spark plug.
Constant direct current creates a stationary magnetic field, which induces zero voltage.

Key Concept

Electromagnetic induction in ignition coils via rapid primary magnetic field collapse
Estimated Time:1m 0s
Question 17Question →

In an automotive electronic ignition system, a sequence of electrical and magnetic events must occur to generate and deliver spark to the cylinder. In what chronological order do these events occur during a single ignition cycle?

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence begins with the crankshaft position sensor detecting rotational position, followed by the control module opening the primary circuit, which causes the primary magnetic field to collapse and induce high voltage, ending with the high-voltage arc across the spark plug gap.
The ignition process always proceeds from sensor detection to primary circuit interruption, followed by mutual induction in the secondary coil, and ends with the spark plug discharge.

Step-by-Step Solution

1
Identify the initial timing trigger.
The crankshaft position sensor signals the engine control module with accurate crankshaft angle data.
The ignition cycle must establish precise piston location before timing calculations can be executed.
2
Determine the switching action that initiates high voltage.
The control module de-energizes the primary circuit switching transistor, interrupting primary current flow.
A steady DC current in the primary winding creates a magnetic field; breaking this current causes the field to collapse.
3
Trace the step-up voltage induction.
The collapsing magnetic field cuts through the secondary windings, inducing high voltage via mutual induction.
The ratio of secondary to primary wire turns multiplies the initial 12-volt battery power into 20,000 to 50,000 volts.
4
Identify the final delivery of electrical energy.
High-voltage electricity travels to the spark plug and jumps the air gap between the center and ground electrodes.
The electrical arc creates the thermal energy required to ignite the compressed gasoline and air mixture.

Key Concept

Electronic ignition timing triggering, primary circuit interruption, and secondary high-voltage mutual induction.
Estimated Time:1m 0s
Question 18Question →

In a waste-spark distributorless ignition system, each ignition coil is connected to two spark plugs and fires them simultaneously. Which of the following explains why the secondary spark does not cause improper combustion in the paired companion cylinder?

Show answer & explanation

Answer: The companion cylinder is on its exhaust stroke containing spent exhaust gases, so no combustible air-fuel mixture is present to ignite.

Answer

The companion cylinder is on its exhaust stroke containing spent exhaust gases, so no combustible air-fuel mixture is present to ignite.
In a waste-spark distributorless ignition system, companion cylinders share a single coil pack. Their pistons move in mechanical tandem, but their combustion cycles are separated by 360 crankshaft degrees. When the ignition coil discharges, one cylinder is at Top Dead Center on its compression stroke with a fresh air-fuel mixture, while the companion cylinder is at Top Dead Center on its exhaust stroke. Because the companion cylinder contains only inert, post-combustion exhaust gases, the spark jumps across the plug gap harmlessly without igniting any fuel.

Step-by-Step Solution

1
Determine the mechanical and cycle relationship between companion cylinders in an engine.
Companion pistons travel up and down in unison, but their four-stroke operating cycles are offset by exactly 360 degrees of crankshaft rotation.
Understanding four-stroke cycle timing is necessary to identify what phase each cylinder is in when a shared coil fires.
2
Evaluate the contents of each cylinder when the shared ignition coil discharges high voltage.
The primary cylinder is at top dead center on compression with a pressurized air-fuel charge, while the companion cylinder is at top dead center on exhaust pushing out inert burned gas.
Since inert exhaust gases cannot burn again, the secondary spark dissipates harmlessly without creating power or causing backfire.

Key Concept

Waste-spark ignition distribution and four-stroke cycle cylinder phasing
Estimated Time:1m 0s
Question 19Question →

An automotive ignition system relies on specialized mechanical and electronic control devices to regulate spark timing and circuit electrical loads. Match each ignition system control component with its primary operating function.

Click a left item, then click its matching right item

Items

Vacuum advance mechanism
Knock (detonation) sensor
Crankshaft position sensor
Ballast resistor

Matches

Show answer & explanation

Answer

Vacuum advance mechanism pairs with advancing timing under light load and high manifold vacuum; Knock sensor pairs with detecting engine vibrations to retard timing; Crankshaft position sensor pairs with monitoring engine speed and piston position for base timing; Ballast resistor pairs with reducing running primary voltage to protect the coil.
Each component serves a dedicated role in ignition control: the vacuum advance mechanism alters timing mechanically under light-load vacuum conditions; the knock sensor protects the engine by retarding timing upon sensing pre-ignition vibrations; the crankshaft position sensor delivers fundamental RPM and piston angle data for electronic ignition timing; and the ballast resistor lowers continuous primary circuit current to safeguard the ignition coil from excess thermal buildup.

Step-by-Step Solution

1
Identify the primary function of mechanical timing modifiers.
The vacuum advance responds to high intake manifold vacuum during light-load cruise to advance spark timing, matching the function of advancing timing under high vacuum.
Leaner cruising mixtures burn slower and require an earlier spark to achieve peak cylinder pressure at the optimal crankshaft angle.
2
Identify the acoustic/vibration feedback device in electronic ignition management.
The knock sensor senses pinging and prompts ignition retardation, matching the vibration-sensing definition.
Detonation creates damaging shockwaves that must be mitigated immediately by delaying spark delivery.
3
Identify the primary rotational reference sensor.
The crankshaft position sensor delivers core rotational speed and piston top dead center data, matching the base trigger timing function.
Electronic ignition systems require real-time crankshaft angle input to know exactly when pistons approach compression TDC.
4
Identify the primary circuit voltage-limiting component.
The ballast resistor lowers operating voltage across the primary windings during run mode, matching the coil heat protection function.
Full battery voltage is used during starting for a strong spark, but continuous 12-14 volts during running would overheat primary coil windings.

Key Concept

Ignition Timing Control and Primary Circuit Regulation
Estimated Time:1m 15s
Question 20Question →

During a routine tune-up on a gasoline engine, a technician notices that the spark plug electrode gaps have worn significantly wider than the factory specification. How does an excessively wide spark plug gap affect the ignition system's operation?

Show answer & explanation

Answer: The ignition coil must generate a higher secondary voltage to jump the gap, increasing the risk of misfire under load.

Answer

The ignition coil must generate a higher secondary voltage to jump the gap, increasing the risk of misfire under load.
An excessively wide spark plug gap increases the electrical resistance across the open space between the center and ground electrodes. To bridge this increased gap, the ignition coil must produce a significantly higher secondary voltage. Under heavy engine acceleration or load—when cylinder pressure is highest—the required firing voltage may exceed the maximum voltage available from the coil, resulting in an ignition misfire.

Step-by-Step Solution

1
Analyze how spark plug electrode gap affects electrical resistance across the plug tip.
A larger gap between the center electrode and ground electrode creates greater dielectric resistance.
Air and compressed fuel-air vapor act as electrical insulators that require sufficient potential difference to ionize.
2
Determine the impact of increased gap resistance on the ignition coil's secondary circuit.
The secondary winding must build to a higher kilovolt level before current can arc across the wider gap.
Secondary voltage rises until it reaches the breakdown voltage required to jump the spark plug gap.
3
Assess the operational consequence on engine performance when required voltage approaches available coil output.
If required voltage exceeds available coil capacity under high engine load, the plug fails to fire, causing an ignition misfire.
High cylinder pressures under load further increase resistance, causing weak or missing sparks when gaps are oversized.

Key Concept

Spark plug gap resistance and secondary ignition voltage demand
Estimated Time:1m 0s
Page 1 / 2Next
Ignition System Practice Questions — Armed Services Vocational Aptitude Battery (ASVAB) | Examkin