Ignition system troubleshooting tips to maximise lifetime

DENSO explains the key to effective combustion and how to accurately diagnose faults in ignition systems

In today’s low emission and high-efficiency engines, the key to effective combustion is a consistent, high-energy ignition output.

The high voltage required for ignition is provided by the Ignition Coil – a type of transformer that features primary and secondary coils of wire wrapped in layers around an iron core.

The role of the Ignition Coil is to transform the low voltage in a car’s battery into the thousands of volts which are used by the Spark Plug to generate sparking. These sparks ignite the air-fuel mixture inside the combustion chamber.

Ignition Coils can sometimes fail before their usual service life due to wear and defects. These could include overheating caused by internal short circuits, vibration, low battery power, defective ignition cables and mechanical damage, to name a few.

There are many signs that there is a fault with the Ignition Coil, including:

No combustion: No combustion occurs because no spark is emitted.

Stalling: The engine stalls but can be restarted.

Poor drivability: Hesitation during acceleration or the engine misfires.

However, there are many ways to effectively manage Ignition Coils and prolong their lifetime, some as simple as paying extra attention when connecting the Ignition Coil to the Spark Plug, as misalignment can cause severe Spark Plug damage.

For the Electronic Ignition Control, the Diagnostic Trouble Code (DTC) engine warning light will probably be turned on, indicating an ignition error – however, this might be caused by another system problem. A visual check should be performed first to assess whether there is mechanical damage, such as cracks and carbon tracks on the Ignition Coil body, any corroded or worn plugs and cables in the wiring, any loss in battery power to the ignition system, or any oil or water contamination.

In the past, ignition systems used a Spark distribution system in which the high voltage generated by an Ignition Coil was distributed to the Spark Plugs by a distributor via ignition wires. Today’s engines feature a Distributor-Less Ignition (DLI) system, so-called as Direct Ignition System (DIS), delivering high voltage directly from the ignition coils to the Spark Plugs.

For engines with an electronic ignition system, DLI systems create a high voltage by using a coil with an igniter (Stick Coil) that is directly mounted onto the spark plugs in the cylinders.

The Ignition (Stick) Coil is a type of transformer, consisting of:

• A primary Coil that changes electrical energy into magnetic energy

• A core that acts as a magnetic circuit to accumulate magnetic energy

• A secondary Coil that converts magnetic flux variations as electrical energy into high voltage

Spark Plugs

Spark Plugs are critical parts that dominate the engine combustion and bear a major responsibility for higher engine performance.

When the high voltage produced by the ignition system is applied between the centre electrode and ground electrode of the spark plug, the insulation between the electrodes breaks down, current flows in the discharge phenomenon, and an electrical spark is generated. This spark energy triggers the ignition and combustion in the compressed air-fuel mixture.

This discharge is of an extremely brief duration (about 1/1000 of a second) and is extraordinarily complex. The role of the Spark Plug is to reliably generate a strong spark between the electrodes accurately at the specified time to create the trigger for combustion of the gas mixture.

If Iridium Spark Plugs are used, engine output and torque will be improved further.

With the superior ignitability of ultra-thin electrodes (0.4mm) in DENSO’s Iridium Spark Plugs, combustion efficiency will be improved, which will in turn clean exhaust emission. Fuel consumption will be improved too, meaning improved mileage and a great bonus for long-distance drivers.