Ignition leads – questions and answers

Ignition leads carry high voltage from the coil to the distributor and spark plugs and suppress radio interference. They should be replaced every 50,000 km or every three years, preferably before winter. Signs of worn leads include hard starting, higher fuel consumption, sooty plugs and hesitation under acceleration.

What is an ignition lead set for?

  • Ignition – a car that runs well is above all an engine in which energy is distributed correctly, so the condition of the ignition lead set is very important. Its job is to carry high-voltage current from the ignition coil to the distributor and from the distributor to the spark plugs.
  • Interference suppression – a stainless steel conductor, spirally wound on a ferromagnetic core, carries high-voltage current without significant energy loss. Interference is absorbed along the entire length of the lead, which means better TV, radio and phone reception and protects the car's electronic equipment.

How long does an ignition lead set last?

In principle, ignition leads do not wear out, but in reality all kinds of factors – sudden temperature changes, humidity, oil, ozone, fuel, vibration and voltage fluctuations – speed up their ageing.

For better performance, ignition leads should be replaced every 50,000 km or every three years, whichever comes first, preferably before winter.

  • Over time – under the influence of these factors, the lead cracks and its surface becomes rough, and the metal terminal oxidises. This leads to poor conductivity and incomplete combustion.
  • What you may notice – higher fuel consumption, hard starting, black deposits on the spark plug electrode, poor engine performance and radio interference.
  • What you cannot see – in the early stages, damage to the lead is not visible. Microscopic cracks cause energy loss.

How can you tell that an ignition lead set is not working properly?

Please note: leads that glow or spark in the dark have not necessarily suffered insulation breakdown or stopped working properly. Their specific construction strongly ionises the surrounding air, causing external electrical discharges. These discharges will not give you an electric shock.

Typical symptoms of faulty ignition leads are:

  • hard starting, especially in cold and damp weather; prolonged cranking drains the battery,
  • excessive carbon dioxide and soot in the exhaust, visible at the tailpipe,
  • noticeable flat spots when accelerating,
  • higher fuel consumption.

What are the consequences of a faulty ignition lead set?

  • Insufficient interference suppression can disrupt the car's electronic equipment (ABS, ignition, airbags, alarm, ESP, etc.).
  • Ignition problems can shorten the life of the catalytic converter.
  • A faulty lead can interfere with radio and phone operation.
  • All these faults increase air pollution.

What is the difference between a single ignition lead and an ignition lead set?

An ignition lead set consists of several leads (usually four or five), depending on the type of engine and the number of cylinders. A single lead is therefore one part of the set.

We always recommend replacing the complete set. Use single leads only in an emergency breakdown.

Why choose SENTECH?

SENTECH ignition leads are made with ferrite-core technology (not to be confused with the low-quality so-called magnetic core), which ensures maximum reliability and very good conductivity. Carefully selected insulating materials prevent breakdown both in the leads themselves and in the rubber boots.

All components are made to the highest standards, as confirmed by ISO 9001 and QS 9000 certification and numerous awards from vehicle manufacturers.

If we choose other products and the ignition lead set does not do its job properly, it can cause:

  • malfunctions of the car's electronic equipment,
  • poor combustion, leading to higher fuel consumption and air pollution,
  • difficulty starting the car.

Only a perfectly made product can prevent these effects. Thanks to their original design and high build quality, SENTECH ignition lead sets reliably solve these problems.

What are the different lead classes for?

Lead classes define the temperature range in which the lead can operate. Depending on the type of engine, a lead that can withstand a lower or higher temperature is needed. See also: technical information and ignition lead facts and myths.

When should high-voltage ignition leads be replaced?

For better performance, ignition leads should be replaced every 50,000 km or every three years, whichever comes first, preferably before winter.

Whether you need high performance, and whether you drive a car or a lorry, domestic or imported, you can fit SENTECH ignition leads with complete confidence.

Be careful! Some manufacturers advertise their products with a longer warranty (even 5 years), which is not justified by the actual durability of their products.

How should an ignition lead set be replaced?

To make sure your new ignition lead set is fitted correctly, please follow these instructions:

  1. Make sure the engine is cold before you start removing the leads.
  2. To keep the leads in the correct order, remove only one lead at a time and fit the new one in its place. Always start with the longest lead. The lead numbers correspond to the cylinder numbers; once the set is fitted, the numbers should follow in sequence.
  3. Remove all clips and lead separators. Hold the rubber boot of the lead – never pull the lead itself. Remove the boot with a twisting motion (avoid using pliers, screwdrivers or any other tools). Use a soft cloth and alcohol to remove any excess grease from the spark plug end or the ignition coil.
  4. Connect the new lead to the spark plug. Route it through all the clips and channels towards the distributor or coil. This keeps the original routing, which is essential to keep the lead away from the exhaust system and other hot areas and from sharp edges.
  5. Place the lead terminal over the matching distributor or coil tower and push it firmly home.

After fitting, check that each lead is properly seated: the metal terminal should noticeably snap into place, with a sound similar to a press stud closing. See also: ignition lead replacement.

What types of ignition leads are on the market?

There are three ignition lead technologies. They differ in the material the core is made of:

  • copper,
  • carbon (so-called silicone, Kevlar leads, etc.),
  • ferrite.

All three technologies do the same job, but the most reliable is the ferrite core used by SENTECH.

Carbon-core technology causes particularly many problems. These leads have a high initial resistance, which makes it harder for a proper spark to form at the spark plug. In addition, the flow of high-voltage current gradually burns away the carbon particles, so the resistance rises further until the lead stops conducting altogether. See also: technical information.

Are SENTECH ignition leads silicone leads?

Depending on the purpose and class of the lead, different materials are used for the inner and outer insulation. Silicone is one of them. Despite its many advantages, however, silicone is not the best material for ignition leads, and its use depends on many factors.

Of course, SENTECH ignition leads do use silicone wherever it is necessary or essential. Materials have to be selected to best meet both technical requirements and customer expectations. See also: ignition lead tips.