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 57, the reader should be able to: • • • Prepare for ASE Engine Performance (A8) certification test content area “B” (Ignition System Diagnosis and Repair) Describe the procedure used to check for spark Discuss what to inspect and look for during a visual inspection of the ignition 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 OBJECTIVES: After studying Chapter 57, the reader should be able to: • • List the steps necessary to check and/or adjust ignition timing on engines equipped with a distributor Describe how to test the ignition system using an oscilloscope 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: automatic shutdown (ASD) relay base timing • burn Kv display • distributor cap • dwell section firing line • firing order intermediate oscillations millisecond (ms) sweep 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: raster • remove and replace (R & R) • rotor gap spark line • spark tester • superimposed tracked coil • transistor-off point • transistor-on point 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 CHECKING FOR SPARK In a no-start condition, first check for secondary voltage out of the ignition coil or to the spark plugs Remove the coil wire from the distributor cap, install a spark tester, and crank the engine A good coil and ignition system should produce a blue spark NOTE: An intermittent spark should be considered a no-spark condition Typical causes of a no-spark (intermittent spark) condition: Weak ignition coil Low or no voltage to the primary (positive) side of the coil High resistance or open coil wire, or spark plug wire Negative side of coil not being pulsed by ignition module Defective pickup coil or module See Figures 57–1 and 57–2 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 57–2 A close-up showing the recessed center electrode on a spark tester It is recessed 3/8 in into the shell and the spark must jump another 3/8 in to the shell for a total gap of 3/4 in 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 57–1 A spark tester looks like a regular spark plug with an alligator clip attached to the shell This tester has a specified gap that requires at least 25,000 volts (25 kV) to fire 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 Always Use a Spark Tester A spark tester looks like a spark plug except it has a recessed center electrode and no side electrode The tester commonly has an alligator clip attached to the shell so it can be clamped on a good ground connection on the engine A good ignition system should be able to cause a spark to jump this wide gap at atmospheric pressure Without a spark tester, a tech might assume that the ignition system is okay, because it can spark across a normal, grounded spark plug The voltage required to fire a standard spark plug when it is out of the engine and not under pressure is about 3,000 volts or less An electronic ignition spark tester requires a minimum of 25,000 volts to jump the 3/4-in gap Remember that an intermittent spark across a spark tester should be interpreted as a no-spark condition Therefore, never assume that the ignition system is okay because it fires a spark plug—always use a spark tester 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 ELECTRONIC IGNITION TROUBLESHOOTING PROCEDURE Troubleshooting any electronic ignition system for no spark: Step #1 Turn ignition on (engine off) and, using a voltmeter or a test light, test for battery voltage available at the positive terminal of the coil If the voltage is not available, check for an open circuit at the ignition switch or wiring Also check the condition of the ignition fuse (if used) NOTE: Many Chrysler group products use an automatic shutdown (ASD) relay to power the ignition coil The ASD relay will not supply voltage to the coil unless the engine is cranking and the computer senses a crankshaft sensor signal This little known fact has fooled many techs 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 Reading the Intermediate Section The intermediate section should have three or more oscillations (bumps) for a correctly operating ignition system Because approximately 250 volts are in the primary ignition circuit when the spark stops flowing across the spark plugs, this voltage is reduced by about 75 volts per oscillation Additional resistances in the primary circuit would decrease the number of oscillations If there are fewer than three oscillations, possible problems include the following: Shorted ignition coil Loose or high-resistance primary connections on the ignition coil or primary ignition wiring 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 Electronic Ignition and the Dwell Section Dwell is not adjustable with electronic ignition, but does change with increasing rpm with many electronic ignition systems This change in dwell with rpm should be considered normal Many EI systems also produce a “hump” in the dwell section, which reflects a current-limiting circuit in the control module These current-limiting humps may have slightly different shapes depending on the exact module used The humps produced by various GM HEI modules differ slightly 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 Dwell Variation (Electronic Ignition) A worn distributor gear, worn camshaft gear, or other distributor problem may cause engine performance problems, because the signal created in the distributor will be affected by the inaccurate distributor operation Many electronic ignitions vary the dwell electronically in the module to maintain acceptable current flow levels through the ignition coil and module without the use of a ballast resistor NOTE: Distributorless ignition systems vary dwell time electronically within the engine computer or 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 Coil Polarity With the scope connected and the engine running, observe the scope pattern in the superimposed mode If the pattern is upside down, the primary wires on the coil may be reversed, causing the coil polarity to be reversed NOTE: Check the scope hookup and controls before deciding that the coil polarity is reversed 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 Acceleration Check With the scope selector set on the display (parade) position, rapidly accelerate the engine (gear selector in park or neutral with the parking brake on) The results should be interpreted as: All firing lines should rise evenly (not to exceed 75% of maximum coil output) for properly operating spark plugs If the firing lines on one or more cylinders fail to rise, this indicates fouled spark plugs 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 Rotor Gap Voltage The rotor gap voltage test measures the voltage required to jump the gap (0.030 to 0.050 in or 0.8 to 1.3 mm) between rotor and inserts (segments) of the distributor cap Select the display (parade) scope pattern and remove a spark plug wire using a jumper wire to provide a good ground connection Start the engine and observe the height of the firing line for the cylinder being tested Because the spark plug wire is connected directly to ground, the firing line height on the scope will indicate the voltage required to jump the air gap between the rotor and the distributor cap insert The normal rotor gap voltage is to kV, and the voltage should not exceed kV 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 SCOPE-TESTING A WASTE-SPARK IGNITION SYSTEM A handheld digital storage oscilloscope can be used to check the pattern of each individual cylinder Some larger scopes can be connected to all spark plug wires and therefore are able to display both power and waste-spark waveforms Because the waste spark does not require as high a voltage level as the cylinder on the power stroke, the waste form will be normally lower See Figure 57–41 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 57–41 A dual-trace scope pattern showing both the power and the waste spark from the same coil (cylinders and 6) Note that the firing line is higher on the cylinder that is under compression (power); otherwise, both patterns are almost identical 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 SCOPE-TESTING A COIL-ON-PLUG IGNITION SYSTEM On a coil-on-plug (COP) system, each individual coil can be shown on a scope and using the proper cables and adapters, the waveform for all of the cylinders can be viewed at the same time Many Ford coil-on-plug systems use a triple-strike secondary spark event The spark plugs are fired three times when the engine is at idle speed to improve idle quality and to reduce exhaust emissions Above certain engine speeds, the ignition system switches to a single-fire event See Figure 57–42 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 57–42 A secondary waveform of a Ford 4.6 liter V-8, showing three sparks occurring at idle speed 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 TROUBLESHOOTING GUIDE The following list will assist technicians in troubleshooting ignition system problems See the chart on Page 689 of your textbook 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 PHOTO SEQUENCE Ignition System Diagnosis 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 PHOTO SEQUENCE Ignition System Diagnosis Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman (cont.) ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY A thorough visual inspection should be performed on all ignition components when diagnosing an engine performance problem Platinum spark plugs should not be regapped after use in an engine A secondary ignition scope pattern includes a firing line, spark line, intermediate oscillations, and transistor-on and transistoroff points The slope of the spark line can indicate incorrect air–fuel ratio or other engine problems 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