LV36 ignition systems(3)

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kap all phase & 6/11/03 11:35 am Page 11 Student Workbook LV36 Ignition Systems (3) LV36/SWB ` Student Workbook for Technical Certificates in Light Vehicle Maintenance and Repair MODULE LV36 IGNITION SYSTEMS (3) Contents Page Introduction Electrical Measurement Equipment: Unit multipliers Multimeter use General fault finding procedures Voltage Electrical faults Open circuit faults High resistance faults Short circuit faults Exercise Short circuits Before the resistance After the resistance and after the switch (earth switched circuit) After the resistance but before the switch (earth switched circuit) 11 Inspection and Other Fault-Finding Techniques 12 Diagnosis without a Code Reader: Progress check 16 24 Code Readers: MODIS™ Progress check 25 25 30 5 7 8 8 10 10 ……… Page Oscilloscope: Cathode-ray tube Screen graticure Oscilloscope operation Progress check 32 33 36 36 41 Vehicle Testing: Ignition timing Exercise Exercise Ignition coil tests Test procedures for a conventional ignition system Exercise Spark plug and high-tension cords tests 43 43 44 46 49 51 10 Integrated Ignition System: Ignition coil Ignition module Battery voltage should be displayed Signal rotor and pick up coil Inspection of vacuum and governor advance 54 54 55 55 57 Hall Effect: Ignition trigger signals – Hall effect 59 59 (Cont.) -1Copyright © Automotive Skills Limited 2003 All Rights Reserved 49 50 LV36: Ignition Systems (3) Issue 58 Page Direct Ignition Systems Diagnosis: Inspection of ignition signal and wiring Progress check 61 63 66 -2Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Introduction Within Phase Ignition Systems, we need to look at diagnostic procedures associated with electronic ignition systems To enable this to be achieved, the workbook will incorporate sections from other phases, to be used as a recap before entering into vehicle diagnosis The use of multimeters and basic diagnosis is taken from Phase Foundation Skills LV02 and short circuit and open circuit diagnosis is taken from Phase Electrical and Electronic Systems LV33 Each of the areas will enable a greater understanding on how to proceed with ignition system diagnosis Electrical Measurement Equipment Selector Hold / AUTORANGE volts, ohms and diodes 10A port Common 300mA port As the name suggests, a multimeter is capable of measuring a number of electrical units/values The selector allows you to choose which value the meter is to measure, such as ‘Volts DC’ and the ports at the bottom of the meter allow for differing connections of the multimeter’s leads when necessary (the red lead only has to be moved when measuring current flow normally) Every type of multimeter normally has a button that enables the technician to choose the maximum value that he wants to measure (the range of the meter) On the example shown, this is the yellow button in the middle of the selector Selecting the smallest range for the circuit that you are working on aids accuracy -3Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue ~ V -V -300mV -A Ω ~ A Starting from bottom left, the electrical values that this multimeter can typically read are: • • • • • • • amps AC amps DC volts AC volts DC 300mV DC maximum ohms diode tester -4Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Unit multipliers One amp is equal to one thousand milliamps, which is written as 1A =000mA One amp is equal to one million micro amps and is written as 1A = 1,000,000 µA One thousand amps is equal to one Kilo amp which is written as 1000A = 1KA One million amps is equal to one Mega amp and is written as 1,000,000A = 1MA All other electrical units use the same multipliers such as 1mV, 1MW Multimeter use 12 v 12 v 12 v A voltmeter displays the difference in voltage between where you put the red probe and where you put the black probe 0v 0v A voltmeter (a multimeter with volts selected) must always be fitted in parallel with the circuit – this means that the circuit is not broken to accommodate the meter; the meter is fitted across the circuit -5Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue 14.4Ω Remember: • Always switch the 0.00Ω circuit OFF first • Always disconnect the component from the remainder of the circuit Close switch An ohmmeter (a multimeter with ohms selected) is always fitted across the component or wire that you want to test Current must not be flowing in the part of the circuit that you are testing as this will seriously affect your readings An ohmmeter measures circuit resistance by applying a known voltage to a circuit from a battery inside its case and measuring the resultant current flow – from these two values it can calculate the resistance using Ohm’s Law in the same way that you have If current is flowing in the circuit from a different source (i.e the vehicle battery) this will seriously affect its calculation Remember: always fit an ammeter in series with the circuit Never connect an ammeter across a resistance; a good ammeter has zero internal resistance An ammeter (a multimeter with amps selected) must be fitted in series with the circuit whose current you want to measure -6Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue This means that the circuit must be broken and the ammeter must be put into the circuit A good ammeter has an extremely small internal resistance so it is important that you take care not to short a circuit out by putting the ammeter across the only resistance in a circuit (provide the current with an easier path to take through the meter) This will at best blow a fuse in the meter and at worst set it alight! General fault finding procedures Diagnosis is a significant part of a vehicle technician’s responsibility With the proliferation of electrical systems on a modern vehicle, an ability to diagnose electrical faults quickly and accurately has become most valued To be able to fault diagnose electrical circuits accurately and quickly, an understanding of voltage is critical This coupled with the correct use of a voltmeter will enable a technician to find virtually any fault Voltage A few voltage rules must be understood and remembered: Voltage is electrical pressure – it ‘pushes’ current around a circuit Voltage will drop across a resistor Volts drop will only occur if current is flowing The amount the voltage drops across a resistor in a circuit is dictated by the comparative value of that resistor i.e its value when compared to that of any other resistors in the circuit The bigger the value of a resistor, the greater the amount of the available voltage will be used by it when compared to the other resistors in the circuit The voltage after the last resistor in a circuit will be volts so long as current can flow If there is only one resistor in a circuit it is also the last resistor and therefore the voltage after it will be zero so long as current is flowing A voltmeter displays the difference in voltage between the position of the red and black probes -7Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Electrical faults To recap, there are three main types of electrical faults These are: Open circuit faults: High resistance faults, and Short circuit faults Open circuit faults This fault causes an incomplete electrical circuit in which no current flows High resistance faults This fault causes the reduction in the flow of electrical current through a circuit component Short circuit faults This is a faulty or accidental connection between two points of different potential in an electrical circuit caused by pushing the load and establishing a path of low resistance through which an excessive current can flow It can cause damage to the components if the circuit is not protected by a fuse -8Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Exercise 1 High resistance fault Key points: - Before bulb: _v - Before A: _v - Before C: _v - After C: _v - Before D: _v - After D: _v - Failed component: _ Consider this circuit as serviceable showing a simple earth switched lamp circuit and in the condition pictured (switch closed or on) Mark on the voltages at all the key points Identify which component has failed Open circuit fault Key points: - Before bulb: _v - After bulb: _v - At E: _v - After E: _v - At the switch: _v - After the switch: _v - At F: _v - After F: _v - Failed component: _ Now consider an open circuit fault in connector E (poor terminal contact) Mark on the voltages at all the key points Identify which component has failed -9Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue • Overheating of the spark plugs also leaves a visible sign on the electrodes The electrodes become glazed with a white appearance This fault is usually caused by incorrect ignition timing, which causes the combustion pressure and temperature to rise excessively Electrode gap When the visual inspection has been carried out the spark plugs must be cleaned if necessary, and then the electrode gap must be checked The electrode gap will vary depending on the type of ignition system and the type of engine with which the spark plug is being used Manufacturers’ specifications must be used for the spark plug gap When the specification for the spark plug gap has been obtained, then the correct feeler blade must be selected and placed in the electrode gap As the feeler blade is placed in the gap there should be a small amount of friction between the blade and the electrode, if the gap is incorrect then the gap must be adjusted Incorrect electrode gap will cause incorrect operation of the spark plug leading to engine misfire After the spark plug has been checked and the electrode gap set, spark checks can be used to check both the high-tension cords and the operation of the spark plugs Remove the spark plugs from the engine, and then refit them to the high-tension cords Hold the spark against the engine or body ground and then turn the engine over A spark should be generated across the electrode gap If a spark is not generated then both the spark plug and the high-tension cords can be substituted with new components one at a time to decide which component is faulty - 52 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Complete this test for all spark plugs, if none of the spark plugs are sparking then the fault is earlier in the ignition system This type of test can also be used to test the operation of the ignition coil and high-tension cord between the coil and distributor Disconnect the high-tension cord that is fitted between the ignition coil and the distributor at the distributor end Hold the metal end of the high-tension cord approximately 10 mm from a good body ground and turn over the engine A good spark should be generated while the engine is turning If no spark is generated then the high-tension cord should be checked for serviceability, and if this is found to be correct then the ignition coil checks should be carried out Ω Checking the serviceability of the high-tension cords is a relatively easy task A resistance check needs to be carried out on each individual high-tension cord both when connected to the distributor cap and removed from it An ohmmeter should be used to this The two test probes from the ohmmeter should be placed one at either end of the high-tension cord and a reading should then be taken This should then be repeated for each of the hightension cords, and a reading of no higher that 25kΩ should be obtained When completed the process must be carried out with the high-tension cords attached to the distributor cap - 53 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Integrated Ignition System Ignition coil Before any inspections can be carried out on the integrated ignition system, the distributor cap must be removed and the wiring disconnected Ω To inspect the primary coil resistance, select the ohmmeter on the multimeter and place the positive and negative probes in the position shown Check the manufacturers’ specification for the resistance that should be obtained Ω The secondary coil can be checked using the same process as the primary coil, just placing the probes where shown Check the manufacturers’ specification for the resistance that should be obtained - 54 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Ignition module V When inspecting the ignition module, the distributor cap must be removed, but the electrics must stay connected The ignition switch must be placed in the on position and a voltmeter used to check the voltage The voltmeter is connected with the positive probe placed on the ignition coil positive, and the negative probe onto the body ground Battery voltage should be displayed V The power transistor within the module should now be checked Using a voltmeter connect the positive probe to the negative terminal of the coil, and the negative probe to the body ground - 55 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue - + To complete the next test a 1.5 volt battery should be connected between the terminals as shown in the diagram If voltage is applied to the transistor for more than five seconds the transistor will be destroyed V - + With the battery connected, connect the positive probe of the voltmeter to the negative terminal of the ignition coil and the negative probe to a body ground The reading should be between and volts If the reading is incorrect then the module should be replaced When the job has been completed the ignition switch should be turned off - 56 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Signal rotor and pick up coil The air gap between the signal rotor and the pickup coil needs to be inspected if problems occur Check the manufacturers’ specification for this clearance Ω An ohmmeter is used to check the resistance of the pickup coil The positive and negative probes should be placed as shown A resistance of between 140 and 180 ohms should be displayed If the reading is incorrect then the pickup coil should be replaced - 57 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Inspection of vacuum and governor advance To inspect the vacuum advance, disconnect the vacuum hoses and connect a vacuum pump to the diaphragm By operating the vacuum pump apply vacuum to the advancer and see if it moves If it does not move replace or repair the vacuum advancer After checking the vacuum advance, replace the vacuum hoses Next, inspect the governor advance, by turning the rotor counter clockwise, and then releasing it The rotor should return quickly in a clockwise direction After this test has been carried out, move the rotor and check for excessive play - 58 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Hall Effect Ignition trigger signals – Hall effect The Hall drum is connected to the distributor shaft When the distributor shaft rotates, the drum rotates The drum has cut-outs; the number of cut-outs corresponds to the number of engine cylinders i.e four cut-outs are used on a cylinder engine + O _ The Hall switch is an integrated circuit (IC), which is affected by magnetism The illustration shows an open/close switch which we will use to represent the Hall IC The Hall switch receives a power supply at the “+” terminal The “-” terminal is connected to earth (usually via the amplifier) The amplifier passes a signal voltage to the “O” terminal (typically between - 10 volts) The amplifier uses any changes experienced in this voltage as a signal to switch the ignition coil on or off - 59 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue High voltage When the solid section of the drum passes between the magnet and the Hall switch, magnetism cannot influence the Hall switch If magnetism cannot influence the Hall switch, the Hall switch will be open When the switch is open, the signal current cannot flow to earth, therefore the signal voltage at Hall switch terminal “O” will be high (and also at the corresponding amplifier terminal.) Switch circuit voltage low – Earth circuit When the cut-out section of the drum passes between the magnet and the Hall switch, magnetism can influence the Hall switch If magnetism influences the Hall switch, the Hall switch will close When the switch is closed, the signal current can now flow to earth The signal voltage at the Hall switch terminal “O” will be zero (and also at the corresponding amplifier terminal) - 60 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Direct Ignition Systems Diagnosis Check the spark plug for sparks Check ignition plug leads Ω The following flowchart will demonstrate some of the tests associated with direct ignition systems We will look at a flow chart for a non-starting engine, although many of the checks could also be related to an engine misfire As with the previous diagnostic flow charts this will take the technician through a set of checks that tests most of the components associated with this system When starting to diagnose this system it is very easy to forget the basics, so begin by testing the spark plugs and high-tension cords Some direct ignition systems not have high-tension cords as the coils are fitted directly to the spark plugs Check the spark plug for sparks Check ignition plug leads Check ignition coils & modules Ω When the spark plugs and high-tension coils have been checked, the ignition coils with modules are next - 61 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue First, disconnect the high-tension cords from the ignition coils Using the ohmmeter section of the multimeter place the positive probe in one terminal, and the negative probe in the other Refer to the manufacturers’ material to obtain the correct reading for that vehicle Reconnect the high-tension cords and carry out a spark test to test the ignition modules Check the spark plug for sparks inspect ignition plug leads inspect ignition coils & modules Ω Inspect camshaft & crankshaft position sensors To inspect the camshaft and crankshaft position sensors, disconnect the sensor connectors and use an ohmmeter to measure the resistance between the terminals - 62 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Inspection of ignition signal and wiring Inspect IGT signal Check for open and short in harness and connector in IGT signal circuit, between engine ECU and ignition coil If open or short found, replace or repair the harness and connector Using the tuition given in the earlier sections of the phase, access the wiring diagram for the vehicle you are working on Find the diagram relating to the ignition system, and identify the wire terminal on the electronic control unit and the connector for the ignition coils and modules Carry out a short circuit and open circuit test on the harness and connector If a fault is found repair or replace the harness or connector Inspect IGT signal Check for open and short in harness and connector in IGT signal circuit, between engine ECU and ignition coil V Check the voltage between the IGT terminal of the engine ECU and body ground Turn the ignition key to the cranking position when carrying out this test After this has been completed, measure the voltage between the ignition signal terminal the electronic control unit and body ground (use the earth terminal on the electronic control unit) The voltage should be more that 0.1 volts and less than 4.5 volts This inspection can also be carried out using an oscilloscope, by checking the waveform between ignition signal terminal, and the earth terminal Both tests should be carried out with the engine turning over If the voltage or signal is incorrect then replace the engine electronic control unit - 63 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue IGT If this test is OK, then disconnect the connector to the ignition coils and check the voltage again between the ignition signal terminal of the electronic control unit and a body ground Check waveform between IGT terminal and earth Disconnect the connectors from the ignition coils and check the voltage between IGT terminal of the engine ECU and a body ground V Turn the ignition key to the cranking position when carrying out this test The voltage reading should be more than 0.1 volts and 4.5 volts If the voltage is incorrect then replace the ignition coils Disconnect the connectors that are connected to the ignition coils Measure the voltage between the power source terminal and a body ground The voltage should be checked with the ignition switch in the on and start position - 64 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Disconnect the connectors from the ignition coils and check the voltage between IGT terminal of the engine ECU and a body ground Check ignition coil power source circuit V Turn the ignition key to the cranking position when carrying out this test Check for open and short circuits in the harness and connector between the ignition switch and the ignition coil Battery voltage should be displayed If the correct voltage is not displayed, the power source circuit should be repaired Check for open and short circuits in the harness and connector between the ignition switch and the ignition coil If a fault is found with the electronic fuel injection main relay then replace it Check the electronic fuel injection main relay Replace the ignition coils Job done If this is found to be OK the next test must be carried out to confirm that there is not an open or short circuit between the ignition switch and the ignition coil Replace or repair the harness or connector if a fault is found Next, test the electronic fuel injection main relay, and if a fault is found then replace it After completing all of the ignition signal tests the ignition coils must be faulty If the tests prior to the ignition signal tests were carried out then a faulty ignition coil would have been found earlier All of the above information should be reinforced with on vehicle testing - 65 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Progress check Answer the following questions: What function of a modern code reader is used to display waveforms? How many vertical and horizontal divisions are there on an oscilloscope screen? What can an oscilloscope be used to measure? If the ignition timing is retarded, what symptoms will the engine demonstrate? - 66 Copyright © Automotive Skills Limited 2003 All Rights Reserved LV36: Ignition Systems (3) Issue ... 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Vehicle Testing Ignition timing Within Phase Ignition Systems, an explanation will be given on how to adjust the ignition timing on an engine... Automotive Skills Limited 2003 All Rights Reserved 49 50 LV36: Ignition Systems (3) Issue 58 Page Direct Ignition Systems Diagnosis: Inspection of ignition signal and wiring Progress check 61 63 66... 2003 All Rights Reserved LV36: Ignition Systems (3) Issue Introduction Within Phase Ignition Systems, we need to look at diagnostic procedures associated with electronic ignition systems To enable