Diagnostics of ignition systems - DIS ignition systems

# DIS ignition systems

Distributor less ignition systems were installed on cars manufactured in the 90's and 00's. These systems use an ignition coil with two secondary towers. One towers is connected to one spark plug using a spark plug wire. The other tower is connected to the companion cylinder. Companion cylinders are the cylinder pair whose piston position is the same. They will be on different strokes. For example, on a 4-cylinder engine, when cylinder ¹1 is on the compression stroke, cylinder ¹4 is on the exhaust stroke. The two spark plugs will fire simultaneously. The spark on the cylinder on the exhaust stroke does not initiate combustion because there is no combustible mixture in that cylinder. This spark, then is wasted.
Another name for a distributor less ignition system is Waste Spark Ignition. One spark plug will fire with the center electrode negative and the other with the ground electrode negative. The cylinder firing with the ground electrode negative will display a slightly higher firing voltage because the ground electrode is cooler than the center electrode.
To find the companion cylinders, take the last half of the firing order and put under the first half of the firing order. For example, a 4-cylinder engine will have a 1-3-4-2 firing order so the companions are 1/4 and 3/2. On a 6-cylinder engine with firing order 1-5-3-6-2-4 the companions are 1/6 , 5/2 and 3/4.
Primary waveform diagnosis.
In order to diagnose the primary ignition it is necessary to connect one oscilloscope probe to the ignition coil negative terminal. The probe must be connected to an analog input ¹5 on the USB Autoscope II. Select "Control => Load user preset => Ignition => Ignition_Primary" in the USB Oscilloscope program. Start the engine. A primary ignition system waveform will be displayed.
The ignition coils may be built as one unit or separate. The ignition control module (ICM) may be underneath the ignition coils, making primary connections for the purpose of obtaining waveforms very difficult. Current ramping may be the best or only choice.
Secondary waveform diagnosis.

- 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 the red capacitive DIS pick ups to the positive firing spark wires as close to the spark plugs as possible.
- Attach the green capacitive pick ups to the negative firing spark plug wires as close to the spark plugs as possible.
- Connect the sync probe Sync (black) to the plug wire for the cylinder ¹1, as close to the spark plug as possible.

Connections for DIS analysis.

- Start the engine.
- In the USB Oscillocope program, select "Control => Load user preset => Ignition => Ignition_Dis".
It may be necessary for correct display to modify the synchronization of the capacitive probe. In the left bottom corner of the USB Oscillocope window press the icon of a hammer and a screw-driver and in the opened window "Setup" to modify the parameter "Cap. sensor synchronization level" so that the waveform is stable.

Normal operating parameters for a DIS (Waste Spark) ignition system are as follows:
- Firing voltage - also known as break down voltage - on the average 4-18 kV;
On the waste cylinder – on the average 3-5 KV;
- Spark voltage - also known as burn voltage 1-4 kV;
- Spark duration - also known as burn time 1-2 ms.
The above values will change according to the air/fuel ratio and cylinder pressure.
Typical DIS ignition system waveforms.
Wiring diagram of a typical DIS (Waste Spark) ignition system.
1. Attachment points for the capacitive DIS Cx probes.
2. Where to attach the sync probe Sync.
3. Connection points for obtaining primary waveforms.
4. Vehicle battery.
5. Ignition switch.
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 the CKP signal. Note: Some CKP's are not referenced to ground, it may be necessary to connect between the two CKP wires.
12. Connection point for the CMP signal. Same note as for CKP apply.
Secondary waveform from a DIS 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. 2 is often called the "current limiter hump".
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 from a DIS 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.
The waveform from the sync probe.
1. Firing spark on the compression stroke.
2. Waste spark on the exhaust stroke.
Waveform from the CKP.
Waveform from the CMP.

# DIS modules

This is a DIS (Waste spark) system where the ignition coils, module and spark plug attachments are incorporated in to one module or cassette.
Access to the primary circuit for the purpose of obtaining waveforms can be difficult or impossible.
DIS module.
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 Integrated DIS ignition module and attach a capacitive ring to each spark plug "wire", and one extra capacitive ring to the "wire" for the cylinder ¹1.

Installing capacitor rings.

- Re-attach the Integrated DIS ignition module, taking care not to damage the capacitor rings.
- Attach the red capacitive DIS pick ups to the positive firing capacitor rings.
- Attach the green capacitive pick ups to the negative firing capacitor rings.
- Attach the sync probe (black) to the capacitor ring for the timing cylinder.
- Start the engine.
- In the USB Oscillocope program, select "Control => Load user preset => Ignition => Ignition_Dis".
It may be necessary for correct display to modify the synchronization of the capacitive probe. In the left bottom corner of the USB Oscillocope window press the icon of a hammer and a screw-driver and in the opened window "Setup" to modify the parameter "Cap. sensor synchronization level" so that the waveform is stable.

# Direct DIS ignition

Some engines are equipped DIS with the ignition coils located directly above the spark plugs. The spark plug directly underneath the ignition is connected directly, the companion cylinder with a plug wire.
Direct DIS ignition.
This is a DIS (Waste spark) system where the ignition coils, module and spark plug attachments may be incorporated in to one or two modules. Access to the primary circuit for the purpose of obtaining waveforms can be difficult or impossible.
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 DIS ignition coils and attach a capacitive ring to each spark plug "wire", and one extra capacitive ring to the "wire" for the cylinder ¹1.
- Re-attach the DIS ignition coils, taking care not to damage the capacitor rings.
- Attach the red capacitive DIS pick ups to the positive firing capacitor rings.
- Attach the green capacitive pick ups to the negative firing capacitor rings.
- Attach the sync probe (black) to the capacitor ring for the cylinder ¹1.
- Start the engine.
- In the USB Oscillocope program, select "Control => Load user preset => Ignition => Ignition_Dis".
It may be necessary for correct display to modify the synchronization of the capacitive probe. In the left bottom corner of the USB Oscillocope window press the icon of a hammer and a screw-driver and in the opened window "Setup" to modify the parameter "Cap. sensor synchronization level" so that the waveform is stable.