Make TOYOTA Model 4A-FE Year ...................
Warning: Ignition coils create high voltage. It can be dangerous, so avoid getting too close to ignition parts when engine is running. Make your connections when the engine is off, and then keep your distance when the engine is running. Even some primary voltage is high enough to stop a “Pacemaker”.
Also: Do not run engines with secondary ignition HT leads “open circuit”. Make sure they are grounded to engine through a spark plug, grounding wire, or spark tester.
If you have problems with the task, see you lecturer for help.
1.0 Primary Voltage Patterns
1.1 Set up a lab scope or ignition oscilloscope to view the primary ignition pattern (in parade or display mode) on your lab scope, with the engine warmed up and idling.
1.2 Record the average Firing Voltage (or “Step Up voltage) for each cylinder in the chart below. Some variation is normal, just pick the average. If you don’t understand what this is, review the resource information available.
1.3 Record the average Burn Voltage for each cylinder in the chart below.
1.4 Record the average Burn Time in milliseconds for each cylinder in the chart below.
1.5 Record the average Dwell Time for each of the cylinders in the chart below. What unit of measurement are you using to measure the dwell time?
7ms
1.6 Are all these primary ignition voltage readings normal? Yes _√__ No ____ Please discuss what is normal or abnormal about this pattern and what causes it?
From the primary ignition pattern, firing voltages were at + 300 v in all cylinders and burn voltages were around 50 v in all cylinders. Next, burn time and dwell time were at 1.5ms and 7ms each in all cylinder. As a result, primary ignition pattern is normal with correct values and four cylinders have similar ignition pattern.
1.7 Draw or photograph the Primary Ignition oscilloscope parade pattern from your scope into the box below. Do it carefully and show the detail you need to see for diagnosis. Record voltage and time scales.
1.8 Discuss what the primary display or parade pattern emphasizes for diagnosis. What can it help you see?
From the above waveform,I can check the 6 stage of ignition pattern in 4 cyclinders.
1 battery supply voltage
2 dwell time
3 firing kv
4 spark burn time
5 continuing
6 isolation
2 is the Dwell part of the pattern. This is where the coil is actually turned on by the vehicle's control module. The coil is building up a strong magnetic field to spark the spark plug during this part of the pattern.
3 is the part of the pattern where the spark is actually firing. The initial spark uses the most voltage, as the spark is generated less voltage is needed to maintain the spark and the voltage drops. The amount of time the spark stays active and the amount of voltage needed to keep the spark going can give you clues as to what's going on inside the cylinder. A low starting spark line could indicate that that the spark plug could be oil fouled, that a short in the spark plug wire is present, or that the cylinder compression is low.
2 is the Dwell part of the pattern. This is where the coil is actually turned on by the vehicle's control module. The coil is building up a strong magnetic field to spark the spark plug during this part of the pattern.
3 is the part of the pattern where the spark is actually firing. The initial spark uses the most voltage, as the spark is generated less voltage is needed to maintain the spark and the voltage drops. The amount of time the spark stays active and the amount of voltage needed to keep the spark going can give you clues as to what's going on inside the cylinder. A low starting spark line could indicate that that the spark plug could be oil fouled, that a short in the spark plug wire is present, or that the cylinder compression is low.
5 to 6 is the part where the coil is turned off and the magnecit field that the coil has generated is now collapsing. You can get an idea what shape your coil is in by watching the osolations just after the spark plug is done firing. If there are fewer than four osolations at this part of the pattern then there could be some shorting in the coil.
reference by http://www.linnbenton.edu/
1.10 Some scopes have the facility to use raster or stacked display. How could this help you to diagnose a fault. What can you see more clearly?
I can control the size of voltage and time and the waveform can be bigger, so I can see more clearly with detail information.
2.0 Secondary Voltage Patterns
2.1 Set up your ignition oscilloscope or lab scope to view the secondary ignition patterns on your lab scope, with the engine warmed up and idling. (Use parade mode or individual mode on each different cylinder, depending on scope available.)
2.2 Record the average Firing Voltage (or “Step Up voltage) for each cylinder in the chart below. Some variation is normal, just pick the average. If you don’t understand what this is, review the resource information at the back of this worksheet.
2.3 Record the average Burn Time for each cylinder in the chart below.
Are all these secondary ignition voltage readings normal? Yes _√__ No ____ Discuss what is happening in the pattern and what it is telling you about the ignition system.
From the secondary ignition pattern, firing voltages were at 2 to 5 kv in cylinders and burn times were at 1.5ms in three cylinders and #4 cyl was at 1.7ms. As a result, secondary ignition pattern is slightly differnt but these patterns are normal with correct values.
2.5 Do a Snap Acceleration (don’t damage the engine by revving too high or for too long) and record in the chart below how high the Firing Voltage (KV) went under Snap Acceleration.
2.6 Are all these Snap Acceleration secondary ignition voltage readings normal? Yes _√__ No ____ Discuss what is happening and what the pattern is telling you.
2.7 Draw or photograph the Secondary Ignition lab scope pattern while idling from your scope into the box below. Do it carefully and show the detail you need to see for diagnosis.
reference by http://www.crypton.co.za/Tto%20know/Ignition/burn%20time.html
2.8 If you can safely do this, (with the engine stopped), gently disconnect one spark plug wire, and short to the engine with a jumper wire. Which cylinder number did you short? __3__
2.9 Start the engine and let it idle (for only a short time.) Record the new Firing Voltage and Burn Time for all the cylinders in the chart below.
2.10 Draw or photograph the shorted Secondary Ignition waveform you see now on your scope.
2.11 Discuss what is happening in the shorted ignition pattern and how the ignition pattern tells you what it is happening in the ignition system.
reference by http://www.linnbenton.edu/
1.10 Some scopes have the facility to use raster or stacked display. How could this help you to diagnose a fault. What can you see more clearly?
I can control the size of voltage and time and the waveform can be bigger, so I can see more clearly with detail information.
2.0 Secondary Voltage Patterns
2.1 Set up your ignition oscilloscope or lab scope to view the secondary ignition patterns on your lab scope, with the engine warmed up and idling. (Use parade mode or individual mode on each different cylinder, depending on scope available.)
2.2 Record the average Firing Voltage (or “Step Up voltage) for each cylinder in the chart below. Some variation is normal, just pick the average. If you don’t understand what this is, review the resource information at the back of this worksheet.
2.3 Record the average Burn Time for each cylinder in the chart below.
Are all these secondary ignition voltage readings normal? Yes _√__ No ____ Discuss what is happening in the pattern and what it is telling you about the ignition system.
From the secondary ignition pattern, firing voltages were at 2 to 5 kv in cylinders and burn times were at 1.5ms in three cylinders and #4 cyl was at 1.7ms. As a result, secondary ignition pattern is slightly differnt but these patterns are normal with correct values.
2.5 Do a Snap Acceleration (don’t damage the engine by revving too high or for too long) and record in the chart below how high the Firing Voltage (KV) went under Snap Acceleration.
2.6 Are all these Snap Acceleration secondary ignition voltage readings normal? Yes _√__ No ____ Discuss what is happening and what the pattern is telling you.
When the snap acceleration is added, the firing voltage slightly increased. This means that higher rpm needs higher firing voltage with short burn time.
2.7 Draw or photograph the Secondary Ignition lab scope pattern while idling from your scope into the box below. Do it carefully and show the detail you need to see for diagnosis.
2.8 If you can safely do this, (with the engine stopped), gently disconnect one spark plug wire, and short to the engine with a jumper wire. Which cylinder number did you short? __3__
2.9 Start the engine and let it idle (for only a short time.) Record the new Firing Voltage and Burn Time for all the cylinders in the chart below.
2.10 Draw or photograph the shorted Secondary Ignition waveform you see now on your scope.
When the spark pulug is shorted, the firing voltage drops to 2 kv and the burn time increases to 2.2ms because there was not a spark gap.
2.12 Remove the ground wire and attach the spark plug wire back on the engine so it is normal again. Run the engine a bit to clear the spark plug.
2.13 Stop the engine and attach a spark tester to another spark plug wire. Start the engine and let it idle (for only a short time). Record the new Firing Voltage and Burn Time for all the cylinders in the chart below.
2.14 Draw or photograph the spark tester Secondary Ignition waveform you see now on your scope. Show the detail that is necessary for accurate diagnosis. Include time and voltages.
2.15 Stop the engine, remove the spark tester (be gentle), replace the spark plug wire, and run the engine to clear the spark plug. The engine should be back to normal now. If not, tell your lecturer.
2.16 Discuss what happens to the ignition waveform when the spark tester is attached to the spark plug wire. What does it tell you about the ignition system.
When the spark tester is located at 20 kv (bigger spark gap) in #4 cyl , the firing voltage increases to 6 kv and the burn time decreases to 1.3ms because there was a bigger spark gap.
As a result, the firing voltage and burn time are related to the spark gap. If spark gap is small the firing voltage will decrease and the burn time will increase. On the other hand, if spark gap is big the firing voltage will go up and the burn time will drop.
2.17 Remove the spark tester carefully, and put everything back together on the engine. Engine runs fine? __√__ yes, or ____ no. If any problems with vehicle, please tell your instructor.
2.12 Remove the ground wire and attach the spark plug wire back on the engine so it is normal again. Run the engine a bit to clear the spark plug.
2.13 Stop the engine and attach a spark tester to another spark plug wire. Start the engine and let it idle (for only a short time). Record the new Firing Voltage and Burn Time for all the cylinders in the chart below.
2.14 Draw or photograph the spark tester Secondary Ignition waveform you see now on your scope. Show the detail that is necessary for accurate diagnosis. Include time and voltages.
2.15 Stop the engine, remove the spark tester (be gentle), replace the spark plug wire, and run the engine to clear the spark plug. The engine should be back to normal now. If not, tell your lecturer.
2.16 Discuss what happens to the ignition waveform when the spark tester is attached to the spark plug wire. What does it tell you about the ignition system.
When the spark tester is located at 20 kv (bigger spark gap) in #4 cyl , the firing voltage increases to 6 kv and the burn time decreases to 1.3ms because there was a bigger spark gap.
As a result, the firing voltage and burn time are related to the spark gap. If spark gap is small the firing voltage will decrease and the burn time will increase. On the other hand, if spark gap is big the firing voltage will go up and the burn time will drop.
2.17 Remove the spark tester carefully, and put everything back together on the engine. Engine runs fine? __√__ yes, or ____ no. If any problems with vehicle, please tell your instructor.
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