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CHAPTER 16Ignition System Componentsand Operation

Automotive Engine Performance, 3/eBy James D. HaldermanCopyright 2010, 2007, 2003 Pearson Education, Inc.,Upper Saddle River, NJ 07458 All rights reserved.*

OBJECTIVESAfter studying Chapter 16, the reader will be able to:Prepare for ASE Engine Performance (A8) certification test content area B (Ignition System Diagnosis and Repair).Explain how ignition coils create 40,000 volts.Discuss crankshaft position sensor and pickup coil operation.Describe the operation of waste-spark and coil-on-plug ignition systems.


KEY TERMSElectronic ignition system (EIS) Electronic spark timing (EST) Flyback voltage Hall-effect switch High energy ignition (HEI) Igniter Ignition coil Ignition control (IC) Ignition control module (ICM) Ignition timing Inductive reactance Initial timing Ion-sensing ignition Iridium spark plugs Knock sensor (KS) Magnetic pulse generator Magnetic sensor Married coil Mutual induction Optical sensors Paired cylinder Pickup coil (pulse generator) Ping Platinum spark plugs Polarity Primary ignition circuit Saturation Schmitt trigger Secondary ignition circuit Self-induction Spark knock Spark output (SPOUT) Switching Tapped transformer Transistor Trigger True transformer Turns ratio Up-integrated ignition Waste-spark ignition


IGNITION SYSTEM OPERATIONThe ignition system includes components and wiring necessary to create and distribute a high voltage (up to 40,000 volts or more). All ignition systems apply voltage close to battery voltage (12 volts) to the positive side of the ignition coil and pulse the negative side to ground. When the coil negative lead is grounded, the primary (low-voltage) circuit of the coil is complete and a magnetic field is created around the coil windings.


IGNITION SYSTEM OPERATIONWhen the circuit is opened, the magnetic field collapses and induces a high-voltage spark in the secondary winding of the ignition coil. Early ignition systems used a mechanically opened set of contact points to make and break the electrical connection to ground. Electronic ignition uses a sensor, such as a pickup coil and reluctor (trigger wheel), or trigger to signal an electronic module that makes and breaks the primary connection of the ignition coil.


IGNITION COILSPURPOSE AND FUNCTIONThe heart of any ignition system is the ignition coil. The coil creates a high-voltage spark by electromagnetic induction. Many ignition coils contain two separate but electrically connected windings of copper wire. Other coils are true transformers in which the primary and secondary windings are not electrically connected.


IGNITION COILSPURPOSE AND FUNCTION


IGNITION COILSCOIL CONSTRUCTIONThe center of an ignition coil contains a core of laminated soft iron (thin strips of soft iron).This core increases the magnetic strength of the coil. Surrounding the laminated core are approximately 20,000 turns of fine wire (approximately 42 gauge). These windings are called the secondary coil windings. Surrounding the secondary windings are approximately 150 turns of heavy wire (approximately 21 gauge). These windings are called the primary coil windings.


IGNITION COILSCOIL CONSTRUCTION


IGNITION COILSCOIL CONSTRUCTION


IGNITION COILSSELF-INDUCTIONWhen current starts to flow into a coil, an opposing current is created in the windings of the coil. This opposing current generation is caused by self-induction and is called inductive reactance. Inductive reactance is similar to resistance because it opposes any changes (increase or decrease) in current flow in a coil. Therefore, when an ignition coil is first energized, there is a slight delay of approximately 0.01 second before the ignition coil reaches its maximum magnetic field strength. The point at which a coils maximum magnetic field strength is reached is called saturation.


IGNITION COILSMUTUAL INDUCTIONIn an ignition coil there are two windings, a primary and a secondary winding. When a change occurs in the magnetic field of one coil winding, a change also occurs in the other coil winding. Therefore, if the current is stopped from flowing (circuit is opened), the collapsing magnetic field cuts across the turns of the secondary winding and creates a high voltage in the secondary winding. This generation of an electric current in both coil windings is called mutual induction.


IGNITION COILSHOW IGNITION COILS CREATE 40,000 VOLTS


IGNITION COILSPRIMARY IGNITION CIRCUITBatteryIgnition switchPrimary windings of coilPickup coil (crank sensor)Ignition module (igniter)


IGNITION COILSSECONDARY IGNITION CIRCUITSecondary windings of coilDistributor cap and rotor (if the vehicle is so equipped)Spark plug wiresSpark plugs


What Is a Married and Divorced Coil Design?An ignition coil contains two windings, a primary winding and a secondary winding, and these windings can be either connected together at one end or kept separated.MarriedDivorced


What Is a Married and Divorced Coil Design?


IGNITION SWITCHING AND TRIGGERINGFor any ignition system to function, the primary current must be turned on to charge the coil and off to allow the coil to discharge, creating a high-voltage spark. This turning on and off of the primary circuit is called switching. The unit that does the switching is an electronic switch, such as a power transistor. This power transistor can be located in any of the following locations:In the ignition control module (ICM)In the PCM (computer)


PRIMARY CIRCUIT OPERATIONTo get a spark out of an ignition coil, the primary coil circuit must be turned on and off. This primary circuit current is controlled by a transistor (electronic switch) inside the ignition module or (igniter) that in turn is controlled by one of several devices, including:Pickup coil (pulse generator)Hall-effect switchMagnetic crankshaft position sensorOptical sensors


PRIMARY CIRCUIT OPERATION
















Optical Distributors Do Not Like LightOptical distributors use the light emitted from LEDs to trigger phototransistors. Most optical distributors use a shield between the distributor rotor and the optical interrupter ring. Sparks jump the gap from the rotor tip to the distributor cap inserts. This shield blocks the light from the electrical arc from interfering with the detection of the light from the LEDs.If this shield is not replaced during service, the light signals are reduced and the engine may not operate correctly. This can be difficult to detect because nothing looks wrong during a visual inspection. Remember that all optical distributors must be shielded between the rotor and the interrupter ring.


Optical Distributors Do Not Like Light


The Tachometer TrickWhen diagnosing a no-start or intermittent misfire condition, check the operation of the tachometer. If the tachometer does not indicate engine speed (no-start condition) or drops toward zero (engine misfire), then the problem is due to a defect in the primary ignition circuit. The tachometer gets its signal from the pulsing of the primary winding of the ignition coil. The following components in the primary circuit could cause the tachometer to not work when the engine is cranking.Pickup coilCrankshaft position sensorIgnition module (igniter)Coil primary wiring


The Tachometer TrickIf the vehicle is not equipped with a tachometer, connect a handheld tachometer to the negative terminal of the coil. Remember the following:No tachometer reading means the problem is in the primary ignition circuit.Tachometer reading okay means the problem is in the secondary ignition circuit or is a fuel-related problem


DISTRIBUTOR IGNITIONGENERAL MOTORS HEI ELECTRONIC IGNITIONHigh energy ignition (HEI) has been the standard equipment DI system on General Motors vehicles. Some models use an ignition coil inside the distributor cap and some use an externally mounted ignition coil. The operation of both styles is similar. The large-diameter distributor cap provides additional space between the spark plug connections to help prevent crossfire.


DISTRIBUTOR IGNITIONGENERAL MOTORS HEI ELECTRONIC IGNITION






DISTRIBUTOR IGNITIONFORD ELECTRONIC IGNITIONFord electronic ignition systems all function similarly, even though over the years the system has been called by various names.The EEC IV system uses the thick-film-integration (TFI) ignition system. This system uses a smaller control module attached to the distributor and uses an air-cooled epoxy E coil.


DISTRIBUTOR IGNITIONFORD ELECTRONIC IGNITION


DISTRIBUTOR IGNITIONOPERATION OF FORD DISTRIBUTOR IGNITIONFord DI systems function in basically the same way regardless of year and name. Under the distributor cap and rotor is a magnetic pickup assembly. This assembly produces a small alternating electrical pulse (approximately 1.5 volts) when the distributor armature rotates past the pickup assembly (stator). This lowvoltage pulse is sent to the ignition module. The ignition module then switches (through transistors) off the primary ignition coil current. When the ignition coil primary current is stopped quickly, a high-voltage spike discharges from the coil secondary winding.The coil current is controlled in the module circuits by decreasing dwell (coil-charging time), depending on various factors determined by operating conditions.


DISTRIBUTOR IGNITIONOPERATION OF FORD DISTRIBUTOR IGNITION


DISTRIBUTOR IGNITIONCHRYSLER DISTRIBUTOR IGNITIONChrysler was the first domestic manufacturer to produce electronic ignition as standard equipment. The Chrysler system consists of a pulse generator unit in the distributor (pickup coil and reluctor).Chryslers name for their electronic ignition is electronic ignition system (EIS), and the control unit (module) is called the electronic control unit (ECU).The pickup coil in the distributor (pulse generator) generates the signal to open and close the primary coil circuit.


DISTRIBUTOR IGNITIONCHRYSLER DISTRIBUTOR IGNITION


WASTE-SPARK IGNITION SYSTEMSWaste-spark ignition is another name for distributorless ignition system (DIS) or electronic ignition (EI). Waste-spark ignition was introduced in the mid-1980s and uses the onboard computer to fire the ignition coils.A four-cylinder engine uses two ignition coils and a six-cylinder engine uses three ignition coils. Each coil is a true transformer in which the primary winding and secondary winding are not electrically connected.Each end of the secondary winding is connected to a cylinder exactly opposite the other in the firing order, which is called a companion (paired) cylinder.


WASTE-SPARK IGNITION SYSTEMS






Odds Fire StraightWaste-spark ignition systems fire two spark plugs at the same time. Most vehicle manufacturers use a waste-spark system that fires the odd-numbered cylinders (1, 3, and 5) by straight polarity (current flow from the top of the spark plug through the gap and to the ground electrode). The even-numbered cylinders (2, 4, and 6) are fired reverse polarity, meaning that the spark jumps from the side electrode to the center electrode.


Odds Fire StraightSome vehicle manufacturers equip their vehicles with platinum plugs with the expansive platinum alloy only on one electrode as follows:On odd-numbered cylinders (1, 3, 5), the platinum is on the center electrode.On even-numbered cylinders (2, 4, 6), the platinum is on the ground electrode. Replacement spark plugs use platinum on both electrodes (double platinum) and can, therefore, be placed in any cylinder location.


IGNITION CONTROL CIRCUITSIgnition control (IC) is the OBD-II terminology for the output signal from the PCM to the ignition system that controls engine timing.Previously, each manufacturer used a different term to describe this signal. For instance, Ford referred to this signal as spark output (SPOUT) and General Motors referred to this signal as electronic spark timing (EST).


IGNITION CONTROL CIRCUITSBYPASS IGNITION CONTROLA bypass-type ignition control means that the engine starts using the ignition module for timing control and then switches to the PCM for timing control after the engine starts. A bypass ignition is commonly used on General Motors engines equipped with distributor ignition (DI), as well as those equipped with waste-spark ignition.


IGNITION CONTROL CIRCUITSBYPASS IGNITION CONTROL


IGNITION CONTROL CIRCUITSBYPASS IGNITION CONTROLThe bypass circuit includes four wires:Tach reference (purple/white). Ground (black/white).Bypass (tan/black).EST (ignition control) (white wire).DIAGNOSING A BYPASS IGNITION SYSTEM


IGNITION CONTROL CIRCUITSUP-INTEGRATED IGNITION CONTROLMost coil-on-plug and many waste-spark-type ignition systems use the PCM for ignition timing control. This type of ignition control is called up-integrated because all timing functions are interpreted in the PCM, rather than being split between the ignition control module and the PCM. The ignition module, if even used, contains the power transistor for coil switching. The signal as to when the coil fires, is determined and controlled from the PCM.


COMPRESSION-SENSING IGNITIONSome waste-spark ignition systems, such as those used on Saturns, use the voltage required to fire the cylinders to determine cylinder position. It requires a higher voltage to fire a spark plug under compression than it does when the spark plug is being fired on the exhaust stroke. The electronics in the coil and the PCM can detect which of the two cylinders that are fired at the same time requires the higher voltage, which indicates the cylinder on the compression stroke. Engines equipped with compression-sensing ignition systems, such as Saturns, do not require the use of a camshaft position sensor to determine cylinder number.


COIL-ON-PLUG IGNITIONCoil-on-plug (COP) ignition uses one ignition coil for each spark plug. This system is also called coil-by-plug, coil-near-plug, or coil-over-plug ignition.The coil-on-plug system eliminates the spark plug wires which are often sources of electromagnetic interference (EMI) that can cause problems to some computer signals. The vehicle computer controls the timing of the spark. Ignition timing also can be changed (retarded or advanced) on a cylinder-by-cylinder basis for maximum performance and to respond to knock sensor signals.


COIL-ON-PLUG IGNITION






COIL-ON-PLUG IGNITIONThere are two basic types of coil-on-plug ignition including:Two-wireThree-wire


Never Disconnect a Spark Plug Wire When the Engine Is Running!Ignition systems produce a high-voltage pulse necessary to ignite a lean airfuel mixture. If you disconnect a spark plug wire when the engine is running, this high-voltage spark could cause personal injury or damage to the ignition coil and/or ignition module.


ION-SENSING IGNITIONIn an ion-sensing ignition system, the spark plug itself becomes a sensor. The ignition control (IC) module applies a voltage of about 100 to 400 volts DC across the spark plug gap after the ignition event to sense the plasma inside the cylinder.


ION-SENSING IGNITION


ION-SENSING IGNITIONThe purpose of this circuit includes:Misfire detection (required by OBD-II regulations)Knock detection (eliminates the need for a knock sensor)Ignition timing control (to achieve the best spark timing for maximum power with lowest exhaust emissions)Exhaust gas recirculation (EGR) controlAirfuel ratio control on an individual cylinder basis


IGNITION TIMINGTHE NEED FOR SPARK ADVANCEIgnition timing refers to when the spark plug fires in relation to piston position.The time when the spark occurs depends on engine speed, and therefore, must be advanced (spark plugs fire some) as the engine rotates faster. The ignition in the cylinder takes a certain amount of time, usually 30 ms (30/1000 of a second).This burning time is relatively constant throughout the entire engine speed range.


IGNITION TIMINGTHE NEED FOR SPARK ADVANCE


IGNITION TIMINGINITIAL TIMINGIf the engine is equipped with a distributor, it may be possible to adjust the base or the initial timing.The initial timing is usually set to fire the spark plug between zero degrees (top dead center or TDC) or slightly before TDC (BTDC). Ignition timing does change as the timing chain or gear wears and readjustment is often necessary on high-mileage engines.


IGNITION TIMINGINITIAL TIMING


KNOCK SENSORSKnock sensors are used to detect abnormal combustion, often called ping, spark knock, or detonation. Whenever abnormal combustion occurs, a rapid pressure increase occurs in the cylinder, creating a vibration in the engine block. It is this vibration that is detected by the knock sensor. The signal from the knock sensor is used by the PCM to retard the ignition timing until the knock is eliminated, thereby reducing the damaging effects of the abnormal combustion on pistons and other engine parts.


KNOCK SENSORSDIAGNOSING THE KNOCK SENSORIf a knock sensor diagnostic trouble code (DTC) is present, follow the specified testing procedure in the service information. A scan tool can be used to check the operation of the knock sensor, using the following procedure.STEP 1 Start the engine and connect a scan tool to monitor ignition timing and/or knock sensor activity.STEP 2 Create a simulated engine knocking sound by tapping on the engine block or cylinder head with a soft-faced mallet.STEP 3 Observe the scan tool display. The vibration from the tapping should have been interpreted by the knock sensor as a knock, resulting in a knock sensor signal and a reduction in the spark advance.


KNOCK SENSORSDIAGNOSING THE KNOCK SENSOR


KNOCK SENSORSREPLACING A KNOCK SENSORIf replacing a knock sensor, be sure to purchase the exact replacement needed, because they often look the same, but the frequency range can vary according to engine design, as well as where it is located on the engine. Always tighten the knock sensor using a torque wrench and tighten to the specified torque to avoid causing damage to the piezoelectric element inside the sensor.


SPARK PLUGSSpark plugs are manufactured from ceramic insulators inside a steel shell. The threads of the shell are rolled and a seat is formed to create a gastight seal with the cylinder head.The physical difference in spark plugs includes:ReachHeat rangeType of seat


SPARK PLUGS


SPARK PLUGS


SPARK PLUGSRESISTOR SPARK PLUGSPLATINUM SPARK PLUGSIRIDIUM SPARK PLUGS


SUMMARYAll inductive ignition systems supply battery voltage to the positive side of the ignition coil and pulse the negative side of the coil on and off to ground to create a high-voltage spark.If an ignition system uses a distributor, it is a distributor ignition (DI) system.If an ignition system does not use a distributor, it is called an electronic ignition (EI) system.A waste-spark ignition system fires two spark plugs at the same time.A coil-on-plug ignition system uses an ignition coil for each spark plug.


REVIEW QUESTIONSHow can 12 volts from a battery be changed to 40,000 volts for ignition?How does a magnetic sensor work?How does a Hall-effect sensor work?How does a waste-spark ignition system work?


CHAPTER QUIZ1.The primary (low-voltage) ignition system must be working correctly before any spark occurs from a coil. Which component is not in the primary ignition circuit?Spark plug wiringIgnition module (igniter)Pickup coil (pulse generator)Ignition switch


CHAPTER QUIZ2.The ignition module has direct control over the firing of the coil(s) of an EI system. Which component(s) triggers (controls) the module?Pickup coilComputer Crankshaft sensorAll of the above


CHAPTER QUIZ3.A reluctor is a ________.Type of sensor used in the secondary circuit.Notched ring or pointed wheelType of optical sensorType of Hall effect sensor


CHAPTER QUIZ4.HEI, and EIS are examples of ________.Waste-spark systemsCoil-on-plug ignition systemsDistributor ignition systemsPickup coil types


CHAPTER QUIZ5.Coil polarity is determined by the ________.Direction of rotation of the coil windingsTurns ratioDirection of laminationsSaturation direction


CHAPTER QUIZ6.Because of ________, an ignition coil cannot be fully charged (reach magnetic saturation) until after a delay of about 10 ms.Voltage drop across the ignition switch and related wiringResistance in the coil windingsInductive reactanceSaturation


CHAPTER QUIZ7.The pulse generator ________.Fires the spark plug directlySignals the electronic control unit (module)Signals the computer that fires the spark plug directlyIs used as a tachometer reference signal by the computer and has no other function


CHAPTER QUIZ8.Two technicians are discussing distributor ignition. Technician A says that the pickup coil or optical sensor in the distributor is used to pulse the ignition module (igniter). Technician B says that some distributor ignition systems have the ignition coil inside the distributor cap. Which technician is correct?Technician A onlyTechnician B onlyBoth Technicians A and BNeither Technician A nor B


CHAPTER QUIZ9.A waste-spark-type ignition system ________.Fires two spark plugs at the same timeFires one spark plug with reverse polarityFires one spark plug with straight polarityAll of the above


CHAPTER QUIZ10.An ion-sensing ignition system allows the ignition system itself to be able to ________.Detect misfireDetect spark knockDetect rich or lean air-fuel mixtureAll of the above

0135093899_pp16a

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