WS8 Primary and Secondary Ignition Patterns

WS8   Primary & Secondary Ignition Patterns

Name: Rata Gemmell  Date:29/06/2011

Make: Toyota   Model: 4A-FE Year: 1995 

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?

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1.6         Are all these primary ignition voltage readings normal? Yes. Please discuss what is normal or abnormal about this pattern and what causes it?
          The firing voltage for each cylinders were 300+ volts and the burn voltage was around 50 volts. The burn time for each cylinder shows 1.5ms and the dwell time is around 7ms. These readings indicate normal primary ignition pattern values therefore they are normal. 
           

Cyl 1	Cyl 2	Cyl 3	Cyl 4	Cyl 5	Cyl 6	Primary Ignition
+300v	+300v	+300v	+300v			Firing Voltage
52v	49v	47v	45v			Burn Voltage
1.5ms	1.5ms	1.5ms	1.5ms			Burn Time
7ms	7ms	7ms	7ms			Dwell Time

     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?
            The primary display patterns help diagnose air/fuel issues and mechanical faults based on the clues visible in this pattern. The above picture numbers the  different elements that make up this pattern and help me see whats going on.
1. Shows the battery voltage.
2. The dwell time shows the primary coil being turned on by the ecu. Inside the primary coil circuit a strong magnetic field of 300+ volts is built up over a period of 7ms. Then when it comes time to fire the spark the ecu opens the circuit. The resulting collapse of the primary coil induces voltage in to the secondary coil windings.
3.shows the firing voltage of 300+ volts which is induced into the secondary coil windings. The firing voltage is a good  pattern for emphasizes on diagnosing problems because it mirrors the secondary coil ignition patterns. If the firing volt readings were high it could be caused by a spark plug with a large gap, a break in an HT lead, worn spark plug or a lean air fuel mixture. The firing voltage will be decreased if a spark plugs gap is too small, low compression in the cylinder, rich air/fuel mixture, incorrect ignition timing or fouled spark plugs. 
4.Number 4 shows the burn time. The burn time is the time the spark is moving across the spark plug gap and should between 1.5ms to 2.0ms. Anything under 0.8ms usually means that a misfire has occured. This helps see into the process of the combustion chamber.           

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?
Raster or stacked display allows me to adjust the voltage size and time. I can also zoom in on the voltage to make more clearly for me too take more accurate readings. 

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.
The secondary ignition pattern shows the firing voltage was 2-5kv along each cylinder and the burn time was 1.5ms for each cylinder. As a result the readings a normal but not correct.  

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.

Cyl 1	Cyl 2	Cyl 3	Cyl 4	Cyl 5	Cyl 6	Secondary Ignition
3kv	2kv	4kv	5kv			Firing Voltage (KV)
1.5ms	1.5ms	1.5ms	1.5ms			Burn Time (ms)
4kv	5kv	6kv	5kv			Snap Acceleration

2.6 Are all these Snap Acceleration secondary ignition voltage readings normal? Yes. Discuss what is happening and what the pattern is telling you.
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 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? Cylinder 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.

Cyl 1	Cyl 2	Cyl 3	Cyl 4	Cyl 5	Cyl 6	Secondary Ignition (one cylinder grounded)
6kv	6kv	2kv	6kv			Firing Voltage (KV)
1.5ms	1.7ms	2.2ms	1.6ms			Burn Time (ms)

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.
The firing voltage in cylinder 3 decreases from 6kv to 2kv becasue the spark plug in cylinder 3 is shorted. This pattern shows what it would look like if a spark plug is leaking or theres a damaged ht lead. The burn time is 2.2ms which is longer than normal. This is because there was no spark gap for  

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.

Cyl 1	Cyl 2	Cyl 3	Cyl 4	Cyl 5	Cyl 6	Secondary Ignition (Spark tester on one cylinder)
4kv	4kv	4kv	6kv			Firing Voltage (KV)
1.5ms	1.5ms	1.4ms	1.3ms			Burn Time (ms)

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. 

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.