start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 56, the reader should 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 Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: bypass ignition coil-on-plug (COP) ignition (also coil-by-plug, coil-nearplug, coil-over-plug) • compression-sensing ignition detonation • distributor ignition (DI) • distributor ignition system (DIS) • divorced coil • dwell e coil • electronic control unit (ECU) • electronic ignition (EI) • electronic ignition system (EIS) • electromagnetic interference (EMI) • electronic spark timing (EST) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: 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 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: paired cylinders • pickup coil (pulse generator) • ping • polarity • primary ignition circuit • primary winding saturation • Schmitt trigger • secondary ignition circuit • secondary winding • self-induction • spark knock • platinum spark plugs • spark output (SPOUT) • switching tapped transformer • transistor • triggering • true transformer • turn ratio up-integrated ignition waste-spark ignition Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The ignition system includes those parts and wiring required to generate and distribute a high voltage to the spark plugs A fault anywhere in the primary (low-voltage) ignition circuit can cause a no-start condition A fault anywhere in the secondary (high-voltage) ignition circuit can cause engine missing, hesitation, stalling, or excessive exhaust emissions Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 IGNITION SYSTEM OPERATION Ignition systems include components and wiring necessary to create  and distribute 40,000 volts or more. All systems apply battery  voltage to the coil positive side, and pulse the negative to ground When the coil negative lead is grounded, the primary (low­voltage)  circuit of the coil is complete and a magnetic field is created around  the coil windings. When the circuit is opened, the magnetic field  collapses and induces a high­voltage spark in the secondary winding  of the ignition coil Early ignition systems used a mechanically opened set of contact  points. Electronic ignition uses a sensor, such as a pickup coil and  reluctor (trigger wheel) to signal an electronic module that makes  and breaks the primary connection of the ignition coil Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 NOTE: Distributor ignition (DI) is the term specified by the Society of Automotive Engineers (SAE) for an ignition system that uses a distributor Electronic ignition (EI) is the term specified by the SAE for an ignition system that does not use a distributor Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 IGNITION COILS The ignition coil creates a high­voltage spark by electromagnetic  induction. Many contain two separate, electrically connected  windings of copper wire.  Figure 56–1 Internal construction of an oil-cooled ignition coil Notice that the primary winding is electrically connected to the secondary winding The polarity (positive or negative) of a coil is determined by the direction in which the coil is wound Other coils are true  transformers in which  primary and secondary  windings are not  electrically connected.  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The center of a coil contains a core of laminated soft iron which  increases magnetic strength of the coil. Surrounding the core are  about 20,000 turns of fine wire (approximately 42 ga.), called the  secondary coil windings Surrounding the secondary windings are approximately 150 turns of  heavy wire (approximately 21 ga.), called the primary coil  windings. The secondary winding has about 100 times the number  of turns of the primary winding, referred to as the turns ratio  (approximately 100:1) In many coils, these windings are surrounded with a thin metal  shield and insulating paper and placed into a metal container to help  retain the magnetic field produced in the windings. Many coils  contain oil to help cool the ignition coil Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 To achieve the goal of having the air–fuel mix completely burned by  the time the piston reaches 10° after top dead center, the spark must be  advanced (occur sooner) as engine speed increases. Timing advance is  controlled by the PCM on most vehicles.  Figure 56–29 Ignition timing marks are found on the harmonic balancers that are equipped with distributor ignition Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 INITIAL TIMING If 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 changes as the  timing chain or gear wears Adjustment is often necessary  on high­mileage engines.  Waste­spark and coil­on­plug  ignitions can’t be adjusted Figure 56–30 The initial timing is where the spark plug fires at idle speed The computer then advances the timing based on engine speed and other factors Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman Continued ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KNOCK SENSORS Knock sensors detect abnormal combustion, called ping, spark  knock, or detonation. When this occurs, rapid pressure increase  occurs in the cylinder, creating vibration in the block, detected by  the knock sensor The PCM uses the signal from the knock sensor (KS) to retard  ignition timing until knock is eliminated, reducing damaging effects  of the abnormal combustion on pistons and other engine parts Inside the sensor is a piezoelectric element that generates a voltage  when pressure or a vibration is applied. The sensor is tuned to a  range from 5 kHz to 10 kHz, depending on engine design. The  signal from the knock sensor is sent to the PCM, which retards  ignition timing until the knocking stops Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Diagnosing the Knock Sensor  If a knock sensor diagnostic trouble  code (DTC) is present, follow specified testing procedure. 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 soft­faced 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 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 A knock sensor can be tested using a digital storage oscilloscope.  Figure 56–31 A typical waveform from a knock sensor during a spark knock event This signal is sent to the computer which in turn retards the ignition timing The timing retard is accomplished by an output command from the computer to either a spark advance control unit or directly to the ignition module Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 NOTE: Some engine computers are programmed to ignore knock sensor signals when the engine is at idle speed to avoid having noise from a loose accessory drive belt, or other accessory, interpreted as engine knock. Always follow the manufacturer’s recommended testing procedure Replacing a Knock Sensor  If 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 Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SPARK PLUGS Figure 56–32 Parts of a typical spark plug Spark plugs are made  from ceramic insulators  inside a steel shell.  The threads of the shell  are rolled A seat is formed to create  a gastight seal with the  cylinder head Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The physical difference in spark plugs includes: Reach  This is the length of the threaded part of the plug Heat range  The heat range of the spark plug refers to  how rapidly the heat created at the tip is transferred to the  cylinder head. A plug with a long ceramic insulator path  will run hotter at the tip than a spark plug that has a  shorter path because the heat must travel further.  Type of seat  Some spark plugs use a gasket and others  rely on a tapered seat to seal See Figure 56­33 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 56–33 The heat range of a spark plug is determined by the distance the heat has to flow from the tip to the cylinder head Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Resistor Spark Plugs  Most spark plugs include a resistor in the  center electrode, which helps to reduce electromagnetic noise or  radiation from the ignition system The closer the resistor is to the actual spark or arc, the more effective  it becomes. The value of the resistor is usually between 2,500 ohms  and 7,500 ohms Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Platinum Spark Plugs  A small amount of the precious metal  platinum welded onto the end of the center electrode gives  platinum spark plugs their name Platinum is a grayish­white metal that does not react with oxygen  and will not erode away as can occur with conventional nickel  alloy spark plug electrodes Platinum is also used as a catalyst in catalytic converters where it  is able to start a chemical reaction without itself being consumed Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Iridium Spark Plugs  Iridium is a white precious metal and is the  most corrosion­resistant metal known. Most iridium spark plugs  use a small amount of iridium welded onto the tip of a small center  electrode 0.0015 to 0.002 inch (0.4 to 0.6 mm) in diameter The small diameter reduces the voltage required to jump the gap  between the center and the side electrode, thereby reducing possible  misfires. The ground or side electrode is usually tipped with  platinum to help reduce electrode gap wear Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY All 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 high­voltage 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 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) A waste­spark ignition system fires two spark plugs at the  same time A coil­on­plug ignition system uses an ignition coil for each  spark plug Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458