WS8 - Primary & Secondary Ignition Pattern

1. Primary Voltage Patterns

Primary coil

Cylinder 1:

burn time = 1.43ms firing voltage = 300v+

dwell time = 7.09ms

burn voltage = 42.6v

Cylinder 2:

burn time = 1.43ms firing voltage = 300v+

dwell time = 6.77ms

burn voltage = 40.7v

Cylinder 3:

burn time = 1.36ms firing voltage = 300v+

dwell time = 6.96ms

burn voltage = 44.4v

Cylinder 4:

burn time = 1.56ms firing voltage = 300V+

dwell time = 6.90ms

burn voltage = 40.7v

Primary Ignition	Cyl 1	Cyl 2	Cyl 3	Cyl 4
Firing Voltage( V )	300+	300+	300+	300+
Burn Voltage( V )	42.6	40.7	44.4	40.7
Burn Time( ms )	1.43	1.43	1.36	1.56
Dwell Time( ms )	7.09	6.77	6.96	6.90

The description of the pattern is in

WS3 - Oscilloscope Patterns to Capture

The reading is not normal. The fire voltage seems too high. Large spark plug gap or high resistance in the circuit may cause this problem.
The pattern can help us to diagnosis the fault in the ignition system, but it just gives us the direction of the faulty area. We need accurate testing to find out fault in the area.
Raster or stacked display can let us compare all cylinders. When engine is old, single pattern of one cylinder shows there is a fault in the system, but if all cylinders are similar, this engine should be fine, maybe just worn and aging.


2. Secondary Voltage Patterns
Idle speed:

Cyl 1: Firing Voltage = 6.4kv Burn Time =1.39ms 

Cyl 2: Firing Voltage = 5.2kv Burn Time =1.32ms 

Cyl 3: Firing Voltage = 6.2kv Burn Time =1.19ms 

Cyl 4: Firing Voltage = 6.1kv Burn Time =1.45ms 

Snap Acceleration:

Cyl 1: Firing Voltage = 9.8kv Burn Time =1.15ms

Cyl 2: Firing Voltage = 8.4kv Burn Time =0.84ms

Cyl 3: Firing Voltage = 9.9kv Burn Time =0.84ms

Cyl 4: Firing Voltage = 9.0kv Burn Time =1.33ms

Secondary Ignition	Cyl 1	Cyl 2	Cyl 3	Cyl 4
Idle Firing Voltage (KV)	6.4	5.2	6.2	6.1
Idle Burn Time (ms)	1.39	1.32	1.19	1.45
Snap Acceleration Firing Voltage (KV)	9.8	8.4	9.9	9.0
Snap Acceleration Burn time (ms)	1.15	0.84	0.84	1.33

The patterns are normal. When snap acceleration, more fuel and air come into the cylinder, the electron need more energy to jump cross the gap of the spark plug, the total energy in the secondary system is the same, then the energy use for burn time is less, so the firing voltage increase and burn time decrease.

3. Short the spark plug wire to engine

Cyl 1: Firing Voltage = 15.4kv Burn Time =0.71ms

Cyl 2: Firing Voltage = 6.1kv Burn Time =1.37ms

Cyl 3: Firing Voltage = 6.1kv Burn Time =1.24ms

Cyl 4: Firing Voltage = 5.3kv Burn Time =1.43ms

Secondary Ignition(one cylinder grounded)	Cyl 1 (grounded)	Cyl 2	Cyl 3	Cyl 4
Firing Voltage (KV)	15.4	6.1	6.1	5.3
Burn Time (ms)	0.71	1.37	1.24	1.43

We can find out which spark plug wire is shorted to ground - Cylinder 1. The firing voltage of cylinder 1 is much higher than other 3 cylinders, because the wire short to engine, the gap between the wire and engine is larger than the spark plug. Need more force(voltage) to push the electrons to jump cross the gap.

4. Spark Tester

Cyl 1: Firing Voltage = 13.9kv Burn Time = 0.74ms

Cyl 2: Firing Voltage = 6.4kv Burn Time =1.41ms

Cyl 3: Firing Voltage = 6.4kv Burn Time =1.34ms

Cyl 4: Firing Voltage = 5.3kv Burn Time =1.12ms

Secondary Ignition(spark tester on one cylinder)	Cyl 1 (spark tester)	Cyl 2	Cyl 3	Cyl 4
Firing Voltage (KV)	13.9	6.4	6.4	5.3
Burn Time (ms)	0.74	1.41	1.34	1.12

Same as the ground test before. More gap, higher firing voltage, shorter burn time. Less gap, lower firing voltage, longer burn time. If the spark plug worn, the gap increase(spark plugs in automobiles generally have a gap between 0.9–1.8 mm), the firing voltage increase, but the burn time shorter, don't have enough time for burn all the mixture in the cylinder, it can cause misfire.