# Shared Flashcard Set

## Details

Automotive Waveforms
Oscilloscope Patterns for Various Circuits
26
Engineering
04/17/2008

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 Cylinder 4
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 Normal Ignition Primary Voltage
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 Firing Line Voltage - This is the voltage needed to initiate the spark. It's normally between 10 to 15 kV.
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 Spark Duration - This is the amount of time that the spark lasts. Normally, this is about 1 to 2 milliseconds.
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 Spark Line - This is the voltage needed to maintain the spark once it's started. It should be flat or slightly upward sloping. Normal voltage is 3 to 5 kV.
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 Inductive Kick - This is an upward swing in the voltage as the spark goes out.
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 Coil Oscillations - These occur as the remaining magnetic field in the coil collapses. There should be 4 to 5 coil oscillations visible and they should taper evenly.
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 Polarity Peak - This occurs when the driver allows current to flow through the primary windings. The time from Point F to point A is the dwell of the coil.
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 Channels:A Sync ProbeB Ignition SecondaryC Cranking CurrentD Knock Sensor VoltageCondition: Normal Cranking
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 Open secondary ignition. Evidence includes firing voltage of over 50 kV, spark duration of less than 1 millisecond, conically diminishing oscillations during the burn time and a firing line that is not a straight vertical spike.
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 ChannelsA: Synch ProbeB: Coil Primary CurrentCondition: Open SecondaryNotice the high inductive kick at the end of the spark event - around 20 A. Also, notice the disorganized noise at the end of the spark event.
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 ChannelsA: Synch ProbeB: Primary Current (parade)Condition: Open secondary on cylinder 3Recall that the firing order is 1-8-4-3-6-5-7-2. Notice cylinder 3's strong inductive kick of around 20 amps. Also, notice the disorganized noise at the conclusion of the spark event.
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 ChannelsD: Ignition Primary VoltageCondition: Open SecondaryNotice the spark line. It's not a straight vertical spike. The duration of the spark appears to be in the appropriate range of 1 to 2 milliseconds, but when compared to healthy cylinders, it is shorter. Notice that during the spark event, voltage drops completely to ground.
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 ChannelsA; Synch ProbeD: Ignition Primary VoltageCondition: Open SecondaryNotice the spark line. It's not a straight vertical spike. The duration of the spark appears to be in the appropriate range of 1 to 2 milliseconds, but when compared to healthy cylinders, it is shorter. Notice that during the spark event, voltage drops completely to ground.
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 Channels:Blue: Synch ProbeRed: Ignition SecondaryCondition: Cylinder 3 Open SecondaryRecall that the firing order is 1-8-4-3-6-5-7-2. Notice the firing voltage of nearly 50 kV. Also, note the short spark duration and high spark voltage.
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 Channels:Gold: Ignition SecondaryShown: Cylinders 5 and 7Condtion: High Secondary ResistanceNotice how the spark line on the right slants down and to the right. This indicates a high resistance somewhere between the rotor and sparkplug. The wave on the left is normal. The cause in this case was a vacuum leak on cylinder 7, causing a lean condition.
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 Channels:Blue: Synch ProbeGold: Secondary IgnitionRed: Injector 1 VoltageGreen: All Injector CurrentNote the high resistance in cylinder number 7. Recall that the firing order is 1-8-4-6-5-3-7-2. This problem was caused by a vacuum leak on cylinder 7.
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 Channels:Red: Injector VoltageGreen: Injector CurrentCondition: NormalNotice that current does not follow voltage immediately, but rather, it "ramps up". This is caused by the inductance of the windings in the injector, as the magnetism lines up the spins of all of the electons. The flat part of the ramp is called current limiting and is achieved by pulse width modulating the voltage as shown in the wave.
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 Channels:Red: Secondary IgnitionCondition: Inoperative Intake ValveWe know that this is secondary because the voltage scale is in kilovolts. Notice that the firing voltage is low at about 6 kV. Also note that the duration is long, approaching 2 milliseconds. These both indicate low overall resistance. In this case, this results from low compression due to an inoperative intake valve. When the vacuum gauge was placed on this engine, the needle fluttered further indicating a problem isolated to one cylinder.
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 Channels:Blue: Sync ProbeGold: Knock Sensor VoltageCondition: Audible TickThis trace shows the knock sensor detecting an audible tick once per engine cycle. This indicates that the noise happens once every other crankshaft revolution, pointing to a problem in the valve train. The timing of the tick is approximately 450 crankshaft degrees after cylinder 1 fires. With further analysis, we were able to determine that this was the #2 intake valve closing
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 Channels:Green: Coil Primary CurrentCondition: NormalNotice the current ramping due to the inductive reactance of the windings in the coil. The flat part of the ramp is current limiting provided by a second driver circuit in the ignition module.
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 Channels:Blue: Sync ProbeGreen: Coil Primary CurrentCondition: NormalNotice the current ramping due to the inductive reactance of the windings in the coil. The flat part of the ramp is current limiting provided by a second driver circuit in the ignition module.
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 Channels:Gold: Primary VoltageCondition: NormalThis trace was conducted with a 20:1 attenuator in line with the probe. Note that voltage starts near 14 and is pulled to ground by the driver in the ignition module. When the driver releases and the coil fires, voltage spikes to approximately 250 volts. Spark line voltage is about 34 volts, and duration is 1.1 milliseconds. On many late model cars, it is impossible to test secondary voltage, so primary voltage is used.
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 Channels:Gold: Primary Ignition VoltageCondition: Shorted SecondaryThis trace looks normal, but observe the duration of the spark. It approaches 3.5 milliseconds. This exceeds the normal 1 to 2 millisecond duration. Also notice the low spark line voltage at approximately 12 volts. All of these clues tell us that secondary resistance is too low.
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 Channels:Red: Secondary Ignition VoltageCondition: Shorted SecondaryThis trace looks normal, but observe the duration of the spark. It approaches 3.5 milliseconds. This exceeds the normal 1 to 2 millisecond duration. Also notice the low spark line voltage at approximately .75 kV. All of these clues tell us that secondary resistance is too low.
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 Channels:Blue: Sync ProbeGreen: Secondary VoltageRed: Injector VoltageGold: Injector CurrentCondition: NormalThese wave traces represent a healthy, normal engine.
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