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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 Probe
B Ignition Secondary
C Cranking Current
D Knock Sensor Voltage
Condition: 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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Channels
A: Synch Probe
B: Coil Primary Current
Condition: Open Secondary
Notice 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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Channels
A: Synch Probe
B: Primary Current (parade)
Condition: Open secondary on cylinder 3
Recall 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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Channels
D: Ignition Primary Voltage
Condition: Open Secondary
Notice 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
A; Synch Probe
D: Ignition Primary Voltage
Condition: Open Secondary
Notice 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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Definition
Channels:
Blue: Synch Probe
Red: Ignition Secondary
Condition: Cylinder 3 Open Secondary
Recall 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 Secondary
Shown: Cylinders 5 and 7
Condtion: High Secondary Resistance
Notice 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 Probe
Gold: Secondary Ignition
Red: Injector 1 Voltage
Green: All Injector Current
Note 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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Definition
Channels:
Red: Injector Voltage
Green: Injector Current
Condition: Normal
Notice 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 Ignition
Condition: Inoperative Intake Valve
We 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 Probe
Gold: Knock Sensor Voltage
Condition: Audible Tick
This 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 Current
Condition: Normal
Notice 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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Definition
Channels:
Blue: Sync Probe
Green: Coil Primary Current
Condition: Normal
Notice 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 Voltage
Condition: Normal
This 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 Voltage
Condition: Shorted Secondary
This 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 Voltage
Condition: Shorted Secondary
This 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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Definition
Channels:
Blue: Sync Probe
Green: Secondary Voltage
Red: Injector Voltage
Gold: Injector Current
Condition: Normal
These wave traces represent a healthy, normal engine. |
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