Ignition coil inspection and testing tips

HELLA consolidates and improves pricing of its OE quality ignition coils

Although not seasonal products in themselves, other factors can contribute to ignition coil breakdown that are often due to the effect of worsening weather on associated components, which in turn put additional strain on the coil and cause it to fail.

Even without any additional strain brought about by challenging weather conditions, ignition coils operate in a demanding working environment where they are subject to high electrical, mechanical, thermal and chemical stress, so they need to be manufactured to the strictest standards, using the highest quality materials to work perfectly and over a long period.

Insufficient output voltage or energy will cause misfiring and incomplete fuel combustion in the cylinder, which can increase the vehicle’s fuel consumption, exhaust emissions and potentially, damage its catalytic converter.

Therefore, if a problem arises, irrespective of the type of ignition coil – single, dual or four-spark or contact/transistor controlled – branches must remind their workshop customers that the correct fault diagnosis is critical and basic principles for the right procedure to assess them, must be followed.

Visual inspection on the vehicle

• Check the ignition coil for mechanical damage
• Check the housing for hairline cracks and sealant leaks.
• Check the electrical wiring and plug connections for damage and oxidation.
Check the electrics using a multimeter or oscilloscope
• Check the voltage supply to the ignition coil
• Check the triggering signal from the ignition distributor, ignition control unit, or engine control unit
Testing with the diagnostic unit
• Read out the fault memory of the ignition system or engine control
• Read out parameters

During all testing work on the ignition system, please note that faults established during tests with the oscilloscope are not necessarily faults caused by the electronic system; they can also be caused by a mechanical problem in the engine.

This may be the case, for example, if compression is too low in one cylinder, which means the oscilloscope shows the ignition voltage for this cylinder to be lower than that of the other cylinders.

Testing the resistance values using the ohmmeter on disconnected coils

Depending on the ignition system and ignition coil design, the following reference values apply: (observe the manufacturer’s specifications)

  • Cylinder ignition coil (transistor ignition system)
  • Primary: 0.5 Ω–2.0 Ω/Secondary: 8.0 kΩ–19.0 kΩ
  • Cylinder ignition coil (electronic ignition system with map-controlled ignition)
  • Primary: 0.5 Ω–2.0 Ω/Secondary: 8.0 kΩ–19.0 kΩ
  • Single-spark or dual-spark ignition coil (fully electronic ignition system)
  • Primary: 0.3 Ω–1.0 Ω/Secondary: 8.0 kΩ–15.0 kΩ

If a high-voltage diode is built into an ignition coil to suppress sparks, it is not possible to measure the resistance of the secondary coil.

In this case, the following method is helpful:

  • Connect a voltmeter in series between the secondary winding of the ignition coil and a battery.
  • If the battery is connected in the diode’s conducting direction, the voltmeter must display a voltage.
  • After reversing the polarity of the connections in the blocking direction of the diode, no voltage must be displayed.
  • If no voltage is indicated in either direction, it can be assumed that there is an interruption in the secondary circuit.
  • If a voltage is indicated in both directions, the high-voltage diode is faulty.

HELLA’s Product & Brand Manager, Matthew Smart, said: “As vehicles continue to change, we work with vehicle manufacturers to develop the technology needed.

“Ignition and engine management is such a crucial element for the correct running of the engine, so to fully assist workshops we transfer this OE knowledge and technology to ensure the aftermarket has the best offering for their customers.

“To ensure their customers can be served quickly and efficiently, we recommend branches keep the most popular references, including the company’s two top selling ignition coils, 5DA 193 175-331 and 5DA 358 000-341, both for Vauxhall applications including Astra, Corsa and Zafira models, on their shelves.

“However, HELLA UK has a 90,000 sq.ft warehouse that allows us to stock a comprehensive range, which provides them with access to the parts they need when their customers need them.”

Naturally, the HELLA electronics range is subject to continuous expansion and new-to-range additions are added on a regular basis, so for more information about the OE products available from HELLA call 01295 662400 or visit www.hella.co.uk.


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