Automotive Technology Course | Ignition Coil and COP Testing

Automotive Technology Course | Ignition Coil and COP Testing


Oh you you you the operation of the ignition coil relies on the principle of induction magnetic fields have the property of inducing a current through a conductor whenever that conductor crosses across the magnetic field lines of flux this is called induction ignition coils used in the automotive industry are actual step-up transformers these coils involved in stepping up the 12 volts produced by the battery to the thousands of volts needed for the spark rely on the principle of induction to produce the actual high-voltage and ignition coil does not generate its own electricity it simply steps up the voltage but at the same time steps down the current by the same numeric factor so on an automotive ignition coil the voltage is going to be stepped up a set amount normally a minimum of 8,000 volts but the current will also be stepped down by the same factor to generate a spark on the newer vehicle the output of some of these coils is close to 45 thousand volts at maximum so again remember that although the voltages stepped up the current is also step-down this is the reason why in less you have a physical problem it is very rare to get injured due to an ignition coil this is not the case with some of the household outlet connected Transformers systems this high voltage produced by the ignition coil is needed to jump the gap at the spark plug and ignite the mixture one side of the ignition coil is tied to the voltage supplied either through a relay or through the ignition switch the other side is connected directly to the ignition control module on some of the newer systems there is no ignition control module the ECM has the internal driver transistor needed to trigger the coil but regardless of how the ignition coil is triggered the operation is still the same which is that it needs to be pulse grounded in order for it to work by pulse grounding the ignition coil and expanding and contracting magnetic field is created made to move across the secondary coil winding and self inducing at high across the secondary components including the spark plugs for ignition let’s see how this works in actual practice notice how the spark is produced when the ignition coil has switched off this is a peculiarities of step-up transformers and transformers in general the reason why is that the high voltages generated when the coil has switched off and the magnetic field is collapsing again the expanding magnetic field self induces our high voltage across the secondary components and the spark plugs this is important to know since all problems found on today’s vehicles especially the ECM internal ignition module types are directly related to how the ignition coil works proper basic testing procedures are still extremely important in the field you can also determine very quickly using the current probe whether the problem is at the ECM coil or ignition control module when you have a problem with the ignition coil and some of these coils may be very expensive you simply don’t have the luxury of using component swap techniques to fix your problem it is not only a simple matter of pricing a new ignition coil into the repair because it will drive the repair order very high besides being dishonest to the customer the more accurate and quicker that you can’t do your Diagnostics the more money you will save the consumer and the more business you will have current ramping the ignition coil will also point out any power feed and ground problems that you may have within the ignition circuit a variant of the newer coil on plug or cough ignition system is the one with an internal ignition module on these the ignition module is usually built right on top of the coil itself you can usually identify this system by the use of three wires at the connector to the coil however not all three wire coils are going to be coil on plug with a built-in ignition module the system is actually fairly simple the three wires out of the connector are the power feed the ground and the trigger wire coming from the ECM this trigger line is a low voltage and current trigger wire do not test this type of trigger wire using a test light often times a 5 volts reference pulse is used to trigger the built-in ignition module do not test low voltage circuits with a test light if you do you’re simply going to live the circuit and the test is not going to work properly to des low voltage circuits you can use the logic probe which is a low voltage digital test light an oscilloscope graphing multimeter or normal voltmeter the current drawn by this type of trigger circuit is very low sometimes 3 wires are used on non built-in ignition module coil on plug systems if this is the case the third wire is used as a feedback for the ECM to know that as farc event has happened consult the wiring diagram before delving into the diagnostic process the ignition timing and well on any cop system is calculated by the ECM and naathan ICM or ignition module in this video clip we are going to show the fastest way to test an ignition coil using different techniques during diagnostics first we will see how the current ramped an ignition coil the first step is to expose the wires to the ignition coil current ramping is very useful since it doesn’t require the technician to break the circuit to do the testing by using an oscilloscope or graphing multimeter attached to a clamp-on amp probe a general determination can be made as to the condition of the various components and circuits in this system this particular coil has a dual wire coil on plug system regular comp ignition systems that do not employ an internal ignition module are a bit easier to test since you only have to contend with two wires once a current waveform is acquired you will know exactly what’s wrong with the circuit or the offending component this may sound as a simplistic test but with enough practice and patience you can turn any ignition or misfire fault into a winner current ramping techniques make for a very powerful way of testing a variety of components throughout a modern automobile let’s take a quick analysis of what an actual coil current waveform will look like on the oscilloscope when analyzing an ignition coil current wave you have to be mindful of the different test points throughout the wave on the bottom waveform you can see a shorted ignition coil this is denoted by the vertical line at the beginning of the pulse this is the beginning of the coil charging face if you look at the upper waveform the slanted line signifies that the ignition coil is slowly charging to its maximum magnetic field output to produce the spark any healthy ignition coil should have this slanted line without any sudden vertical spots the slanted line at the bottom signifies that a few of the ignition coil windings are actually shorted this will be inevitably translate into a lower kV spark value an O start or a misfire the sudden current surge is what gives this vertical tell-tale sign at the beginning of the wave pulse further up the bottom waveform we then see that the line slants again into its normal expanding magnetic field the actual space between the beginning and end of the horizontal zero line is the ignition coil dwell period so in summary whenever analyzing an ignition coil current waveform always look for a slanted line with no sudden vertical spots another point of interest along the waveform is the ability of the ignition module to provide the proper amount of current for the coils magnetic built up this you know by measuring the voltage at the highest point along the wave or at the top of the crystal keep in mind that you are reading a current value translated into a voltage wave the clamp on amp probe does exactly that which is convert an expanding magnetic field produced by the amount of current flowing through the circuit into a voltage signal that the digital oscilloscope can read most coils will draw between 4 to 6 amps depending on the manufacturer so again we are looking for that slanted line at the beginning of the charge cycle and at the same time you are also looking for the ability of the ignition module to provide the right amount of current to trigger the spark at this point in time we are using the snap-on Vantage to make our necessary measurements this is actually a very simple test and consists of clamping the amp probe around either of the two ignition coil wires connecting it to the graphing multimeter and properly analyzing the wave after powering the graphing multimeter zero out the clamp on amp probe to prevent to scoot readout and proceed to make the necessary measurements by going to waveform viewer and choosing our low-frequency digital signal we can immediately Center the wave on screen for later analysis we know that this particular clamp on amp probe will give us a value of under 1 volts so we set our equipment accordingly after zeroing out to clamp on amp probe and setting our equipment proceed to start the vehicle to get a wave temperature following we see the actual ignition coil current waveform produced by this particular Ford vehicle Ford uses a system of coil activation called multiple discharge this system started out in the 70s as a racing inspired ignition system and eventually trickle down into production vehicles a very fast triple-pulse spike is delivered to the ignition coil to trigger the spark plugs this triple ignition pulse only happens at idle and it is done to improve low-end torque at idle speed the Ford multiple pulse ignition system will actually revert into a single pulse at higher rpms we can see here that in this trip will discharge the first pulse is nice and slanted as previously explained the second pulse looks more like a defective coil unit this is normal in Ford ignition systems due to the fact that the magnetic field hasn’t completely collapsed before the second and third ignition pulses again whenever current ramping a Ford ignition system always used the first ignition pulse as a guide remember that this system is only employed by the Ford Motor Company family of vehicles and in this regard the second and third pulses are void of any current ramping information in this particular case we don’t have a problem and we do have a smooth rising magnetic field buildup in the coil unit if you look very carefully at the highest part of the quest you can tell right away the amount of current carrying capacity of the ignition module or ECM in our case a cop ignition system is triggered directly by the ECM internal transistor most of the newer vehicles using coil on plug systems trigger the ignition coils directly at the ECM and no ignition module is employed so by analyzing this ignition current waveform you can ascertain whether the ignition coil is at fault whether you have a problem with the ignition module power feed routes or excessive resistance in the wires and a sulfated connector which would have increased the amount of resistance in the circuit would have lowered the amount of current delivered by the ignition module in such cases a deeper diagnostic routine may be needed to pinpoint the problem so if there had been higher resistance in the circuit a current value of between 4 to 6 amps would have never been present this technique takes a little bit of practice but once properly employed can yield great results during Diagnostics following we proceeded to capture the waveform freeze it and proceed to make the necessary measurements at our leisure after centering the waveform on screen simply pressed the freeze button to store the waveform in memory we can now see the slanted line corresponding to the first ignition pulse as we said before if the slanted line is not present then it is a very good indication that the ignition coil has shorted if the highest point on the pulse is too low then it is also an indication of excessive resistance in the circuit or that the ignition module cannot supply the right amount of current for the coil to operate properly after expanding the amplitude setting on the graphing multimeter we can see the wave in better detail again by measuring the tip of our waveform we can actually see 0.495 volts remember that this is the translated value of a clamp-on amp probe into a voltage by multiplying this value by the setting on the clamp on amp probe we arrived at 4.9 amps which is almost 5 amps this coil is actually drawing almost 5 amps and the ignition control module our computer is providing the right amount of current for this coil to operate as said before most ignition coils will draw between 4 to 6 amps so with a 5 amp supply you would not have a problem with the ignition module if instead you would have had a single pulse that looks like the second pulse on screen then it is a good indication that the ignition module was in good condition but that the coil was shorted remember that this being a Ford vehicle has a multiple discharge spark system and the second and third pulse will always look like a shorted ignition coil a word of caution is that of the tachometer connected to the coil wire if the tachometer is shorted it will show up on the current waveform as a shorted coil often times a shorted tachometer will short the spark completely and make the engine not start you you


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