Replacement of spark plugs

Replacement of spark plugs: plug

The spark plugs of the engine are responsible for the ignition of the air-fuel mixture. If they are impaired in their operation, this has a major impact on the combustion cycle in the engine. The result is misfiring, as well as increased fuel consumption. shows you how to change the spark plugs yourself and save yourself the workshop visit.

Understanding the spark plug

Replacement of spark plugs: replacement

spark plug

The spark plug itself is a small but very important component and is located on each cylinder of a motor vehicle. The ignition coil generates with the ignition interrupter an ignition pulse in the range of approx.15,000 to 30,000 V, which is forwarded to the candle via the ignition cable. At the spark plug, we then generate a spark, which jumps from the ceramic insulated center electrode on the ground electrode and is discharged through the thread. In this way the combustion process is started.

Spark plugs are self-cleaning elements, but only one worksSelf-cleaning temperaturebetween 360 and 850° C. At these temperatures, impurities are burned, which could otherwise lead to the risk of short circuit or shortened spark gap at the electrodes.

A distinction is made between cold and warm spark plugs, with the cold at the center electrode have a short Isolatorfuß and thus can deliver heat faster to the cylinder head. Warm spark plugs, in contrast, have a longer insulator foot, which has a poorer heat-conducting effect, but theSelf-cleaning temperature ensures.

When the material is made of the spark plugs, the insulator is usually alumina, a very brittle ceramic and the electrodes are iron-nickel-chromium alloys with copper core. In addition, platinum, silver and iridium are also used for the electrodeslonger life (up to 100,000km).

Which spark plug?

Replacement of spark plugs: plug

Spark plug from NGK

The sizes of Spark plugs are standardized in Germany and differ in their length, the diameter, and the pitch of the spark plug thread.

In addition, it is important to note whichheat value fits to its engine to ensure optimal operation.

With the help of hervehicle documents can find the correct spark plug based on the chassis and model number. Often, retailers also find little booklets in which they can look up the right spark plugs.

Furthermore, one should buy do not put on the cheapest product, but if possible select a platinum or iridium candle from brand manufacturers such as Bosch, NGK or Beru. These spark plugs convince with good quality and high mileage.

Where are the spark plugs?

To check or replace the spark plugs, they should know where they are in the engine compartment. Depending on the manufacturer and design of the engine may vary the position of the spark plugs and be replaced by other parts such as e.g. be covered the air filter box.

Orient yourself to the ignition cables, which lead from the ignition coil to the individual cylinders and tell them the positions of the individual candles.

Replacement of spark plugs: plugs

Engine compartment with ignition cables

Inspection and replacement of spark plugs

Replacement of spark plugs: plug

spark plug wrench

To test the spark plugs they must first be removed. For this purpose they should disassemble disturbing attachments, which complicate the work, if possible. Then remove the spark plug connector and should already be able to see the spark plug. To unscrew these, a ratchet with extension and a long nut (usually 16mm or 21mm) or a special spark plug wrench with joint is needed. Turn the spark plug counterclockwise and remove it from the socket.

When checking the candle, the following things should be considered:

  • Check the thread and upper contact for corrosion
  • Check insulation material for cracks and burn marks
  • Testing the center electrode for wear
  • Check the spark plug image of the electrodes

The spark plug image is usually the most meaningful indication of the condition of the spark plug during the inspection. For a well-functioning motor, the area around the electrodes should be "fawn brown".

More spark plug pictures can be found at

Replacement of spark plugs: plug

Spark plug wrench insert / Nut

If the candles need to be changed, because they have a bad spark plug image, they do the following:

Screw the new candles clockwise into the sockets, but at the same time be sure to pay attention to the permitted torque, which you can ask the manufacturer. Ideally, the spark plugs are tightened with a torque wrench, but if none is available, a 1/4 turn or 90° turn of the spark plug is a rule of thumb.

Then be the candle plugs put back on and checked the ignition cables. After mounting the remaining attachments, start the engine and check for concentricity.

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Video Board: Spark Plug Replacement DIY (the ULTIMATE Guide)