Diagnostics of ignition systems - COP ignition

# Coil on Plug (COP) ignition

This system use one ignition coil for each cylinder. Most if not all late model cars use this system. The ignition coil, in the majority of the cases, are mounted directly above the spark plugs.
These ignition coils have a lower turns ratio (70:1 as compared to about 100:1). This is done to make these ignition coils more compact. The induced primary voltage will be higher than in other types of ignition coils. Because they have less inductive reactance, the primary current will increase more rapidly than in other ignition coils. When the primary current is turned on, a small (1-2 KV) voltage will be induced in to the secondary. This voltage is higher than in other types of ignition coils. Since there is only one spark gap as opposed to distributor and DIS ignition, it is possible for this voltage to cause a spark at the spark plug. This could cause combustion to start too early and cause backfire and/or engine damage. A high voltage diode is installed in the secondary circuit to prevent this spark (additionally, the high voltage diode will limit oscillations which serve no purpose and will cause heating of the ignition coil). The secondary waveform will differ in appearance on this system, compared to other systems, especially if the pattern is obtained using capacitor rings. A capacitive plate attached to the ignition coil will give good patterns, however, the voltage reading will probably be low.
Obtaining primary waveforms.
It will be necessary to obtain waveforms from each ignition coil individually. Note that many of these ignition coils have the switching transistor - usually an IGBT (Insulated Gate Bipolar Transistor) built in and the primary circuit may be unavailable.
Connection to a primary circuit COP ignition.
Select "Control => Load user preset => Ignition => Ignition_Primary" in the USB Oscilloscope program.
Obtaining secondary waveforms.

- Disconnect all leads from the USB Autoscope II.
- Connect power supply wiring for the ignition system adapter Ignition Adapter to the vehicle battery (red to positive, black to negative).
- Connect the ignition system adapter to the USB Autoscope II.
- Unbolt ignition coils and attach a capacitive ring to the spark plug "wire", and one extra capacitive ring to the "wire" for the cylinder №1.

Capacitor ring installation.

- Re-attach the ignition coil, taking care not to damage the capacitor rings.
- Attach the red pick up lead to the capacitor ring. Remember that the pattern from the capacitor ring will be different due to the presence of a diode in the secondary circuit. Or attach a capacitor plate to the ignition coil, then attach the red pick up to the plate
- Attach the sync probe (black) to the capacitor ring for the cylinder №1.
- Start the engine.
- In the USB Oscillocope program, select "Control => Load user preset => Ignition => Ignition_Cop".
Alternatively, obtain a set of spark plug wires. Attach these between the ignition coils and the spark plugs. Attach your probes as you would for a DIS system.

It is possible to install one capacitor ring on each "plug wire" on each ignition coil, and one extra on the timing cylinder if it is desired to look at a parade of all cylinders. However, remember that the pattern will be distorted.
Typical waveforms from COP ignition.
Wiring diagram for COP ignition.
1. Attachment points for obtaining secondary waveforms using capacitor plates.
2. Attachment point for obtaining a sync signal using a capacitor ring.
3. Attachment points for obtaining primary waveforms. Note: the power transistor may be built in to the ignition coil.
4. Vehicle battery.
5. Ignition switch. Note: may use a relay for ignition power.
6. Ignition coils.
7. Crank Shaft Position (CKP) sensor. It is a Variable Reluctance Sensor (VRS).
8. Cam Shaft Position (CMP) sensor. VRS-type.
9. Spark plugs.
10. The engine control module (ECM), with built-in ignition control module (ICM).
11. Connection point for obtaining a CKP signal. Note: it may be necessary to connect between the two wires, the CKP signal may not be referenced to ground.
12. Connection point for obtaining a CMP signal. Note: It may be necessary to connect between the two wires, the CMP signal may not be referenced to ground.
13. High voltage diode.
14. Attachment points for obtaining secondary waveforms using capacitor rings.
Secondary waveform from a COP system. Captured using a capacitor ring.
1. The transistor turns off and a high voltage is induced. The height of the firing line represents the voltage needed to initiate a spark (cause ionization or break down of the spark gap).
2. The spark line. The height represents the voltage needed to sustain the spark and the length of the line the duration.
3. The spark is extinguished.
Because the high voltage diode does not conduct in the "backwards direction", the sections of the pattern representing primary turn-on and oscillations are not visible in the waveform.
Secondary waveform from a COP system. Captured using a capacitor plate.
1. The transistor in the ICM turns on, primary current starts to flow and a magnetic field is being built up in the ignition coil.
2. The ICM limits the primary current once a predetermined value is reached. Commonly 6-8A.
3. The transistor turns off and a high voltage is induced. The height of the firing line represents the voltage needed to initiate a spark (cause ionization or break down of the spark gap).
4. The spark line. The height represents the voltage needed to sustain the spark and the length of the line the duration.
5. The spark is extinguished. The beginning of the intermediate section with some dampened oscillations.
Primary voltage waveform in a COP ignition system.
1. The transistor in the ICM turns on, primary current starts to flow and a magnetic field is being built up in the ignition coil.
2. The ICM limits the primary current once a predetermined value is reached. Commonly 6-8A.
3. The transistor turns off and a high voltage is induced. The height of the firing line represents the voltage needed to initiate a spark (cause ionization or break down of the spark gap).
4. The spark line. The height represents the voltage needed to sustain the spark and the length of the line the duration.
5. The spark is extinguished. The beginning of the intermediate section with some dampened oscillations.

# COP modules

The COP ignition coils can be incorporated in to modules situated directly above the spark plugs and consisting of from 2 to 6 ignition coil.
COP module.
The switching transistors can be built in to the module or the ignition coils themselves, making it very difficult to obtain primary waveforms.
Obtaining secondary waveforms.

- Disconnect all leads from the USB Autoscope II.
- Connect power supply wiring for the ignition system adapter to the vehicle battery (red to positive, black to negative).
- Connect the ignition system adapter to the USB Autoscope II.
- Unbolt the COP modules and attach a capacitive ring to each spark plug "wire", and one extra capacitive ring to the "wire" for the cylinder №1.
- Re-attach the COP modules, taking care not to damage the capacitor rings.
- Attach the capacitive pick ups to the capacitor rings.
- Attach the sync probe (black) to the capacitor ring for the cylinder №1.
- Start the engine.
- In the USB Oscillocope program, select "Control => Load user preset => Ignition => Ignition_Cop".
- в окне программы выбрать "Управление => Загрузить настройки пользователя => Ignition => Ignition_Cop".
Alternatively, obtain a set of spark plug wires. Attach these between the COP ignition coils and the spark plugs. Attach your probes as you would for a normal ignition system.
It is possible to install one capacitor ring on each "plug wire" on each ignition coil, and one extra on the timing cylinder if it is desired to look at a parade of all cylinders. However, remember that the pattern will be distorted.

# COP ignition using individual spark plug wires

In some cases coil on plug ignition are used, incorporating spark plug wires. These systems usually have the ignition coils incorporated in to one or two modules.
The switching transistors can be built in to the module or the ignition coils themselves, making it very difficult to obtain primary waveforms.
Obtaining secondary waveforms.
Note: Due to the high voltage diode built in to the ignition coils, the waveform obtained from the spark plug wires will be distorted, similar to other COP systems. It is, therefore, recommended to use the capacitor plate(s) and attach these to the ignition coils themselves.

- Disconnect all leads from the USB Autoscope II.
- Connect power supply wiring for the ignition system adapter Ignition Adapter to the vehicle battery (red to positive, black to negative).
- Connect the ignition system adapter to the USB Autoscope II.
- Attach capacitor plate(s) to the ignition coil(s).
- Attach the red pick up lead(s) to the capacitor plate(s).
- Attach the sync probe (black) to the capacitor ring for the cylinder №1.
- Start the engine.
- In the USB Oscillocope program, select "Control => Load user preset => Ignition => Ignition_Cop".

It is possible to install one capacitor ring on each plug wire, and one extra on the timing cylinder plug wire if it is desired to look at a parade of all cylinders. However, remember that the pattern will be distorted.