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Function of a spark plug
The gasoline engine contains a mixture of air and fuel that can be ignited. The ignition voltage generated by the ignition coil is transmitted to the spark plugs, whereupon an ignition spark is created between the two electrodes of a spark plug. This results in a small explosion in the engine compartment, which causes the pistons to move. Subsequently, the engine begins to run. In total, a spark plug fires approximately between 500 and 3,500 times in one minute. For such a small spare part, that's a lot of stress.
In order for the engine to function correctly, properly functioning spark plugs are indispensable. Therefore, you should never underestimate them and replace them regularly within the replacement intervals prescribed by the vehicle manufacturer. The information regarding the replacement intervals can be found in the vehicle manual of your vehicle. Should malfunction symptoms already occur before, you must change the spark plugs earlier. Only spark plugs with platinum center electrode or iridium electrodes as among others in some NGK spark plugs and Bosch spark plugs have a longer life.
How can you tell when a spark plug is defective?
With spark plugs it is a wearing part, because they wear out over time. This happens because as the spark is transmitted, microscopic particles also become detached, increasing the distance between the ground electrode and the center electrode over time. After many thousands of kilometers, the spark can then no longer jump. Indicators for a defect of one or more spark plugs can be, among others, the following:
- Increase of Co² in the exhaust gas
- Sluggish engine start (starter works, but engine does not start / starts after long starter operation)
- Engine jerks / vibrates while driving and more noticeable at idle
- Deterioration of engine performance
- Increased fuel consumption
- Sensing ignitions even during operation
The higher the quality of a spark plug, such as Bosch spark plugs or NGK spark plugs, the longer it takes for them to wear out. In addition to normal wear, a faulty setting in the engine can also cause a spark plug to wear out more quickly. For this purpose, a visual inspection of the spark plugs at regular intervals is sufficient. Your so-called plug image provides information about whether and what defect is present:
- Head of spark plug is fawn: all is well
- Center electrode is completely or partially burned off: inferior fuel, wrong or decomposing additives in fuel and or oil, defective valves
- Spark plug mechanically broken: spark plug too long or due to deposits of metal chips
- Upper part is sooted or electrodes fused together: spark plug is too cold in operation and does not burn all of it, fuel mixture too rich, mainly used only for short trips, dirty air filter, lead deposits may occur if fuel is too high in lead
- Upper part is encrusted: Deposits of oil residue due to incorrect engine oil or engine settings
- Spark plug oily: leaking piston rings or spark plug, oil level too high and therefore too much engine oil in combustion chamber
- Spark plug white or melted: plug has become too hot, for example, due to a fuel mixture that is too lean
For all the above points, the spark plug change only treats the symptoms, but not the causes. The exact cause should finally be determined and remedied by trained professionals, so that the next spark plug change again only in the regular change interval needs to take place.
What to consider when buying spark plugs?
Whoever wants to buy a spark plug should always make sure that it has the right length and thread size. Likewise, the electrode gap and the heat value are important. It is best to first select the vehicle or search by the part number of the previous spark plug. With the results then still pay attention to the restrictions and already the correct spark plug is found.
In general, the search results show spark plugs from several brand manufacturers. For us, it is the following manufacturers:
All spark plugs offered by us are in OEM quality and are partly installed directly by the vehicle manufacturers ex works. In addition to the Bosch spark plugs and NGK spark plugs also convince the others with a high load capacity and a long service life. Therefore, it is worthwhile to rely on brand quality when buying spark plugs.
What to consider when changing spark plugs?
The spark plug change should always be carried out exclusively when the engine is cold. Before it comes to the exchange of the spark plugs, the high-voltage line of the ignition should necessarily be disconnected or switched off. In older cars, the spark plug change can be done without much effort, because there is direct access to the spark plugs. After opening the engine hoods, you can look directly at the spark plug connectors and do not have to dismantle any other components beforehand. Meanwhile, in newer cars, the fairing still has to be removed first.
The individual spark plug connectors are each assigned to a cylinder fixed and should therefore be reattached to the correct cylinder after the spark plug change. To avoid confusion, the plugs should be numbered beforehand, if there is still no clear assignment. The spark plug connectors can then be removed. After removing the plugs, the upper part of the spark plug can be seen, consisting of the connecting nut, the ceramic sheathing and the hexagon nut. To prevent dirt from getting into the cylinders after unscrewing the plugs, the spark plug well should be blown out with compressed air before unscrewing the spark plugs.
Next, the spark plug wrench is placed on the tightening nut and the spark plug is unscrewed with care,so that the thread in the cylinder head is not damaged. Subsequently, dirt in the area of the spark plug hole should be removed and the new spark plug carefully screwed in by hand. It is essential to ensure that the thread is screwed in correctly.
Now, using a torque wrench and the corresponding socket for spark plug wrench, tighten the spark plug to the correct tightening torque. Here it should be noted that the torque wrench also covers the correct Newton meter range (Nm). The correct torque is mandatory to perform according to the manufacturer's instructions with the torque wrench. Too low a tightening torque can possibly cause a loss of compression, as the spark plug does not seal the combustion chamber correctly. Breakage of the ceramic spark plug insulator is also possible, which can damage the piston, resulting in engine damage. Tightening the spark plug too tightly is also fatal. Here, on the one hand, the thread can be damaged in the worst case, the cylinder head.
Therefore, it is advisable to have the spark plug change performed by qualified personnel. Otherwise, it is necessary that you are informed professionally and properly before the assembly. When changing spark plugs, the installation instructions must be followed and the prescribed tightening torques must be observed.
If you have any further questions about changing spark plugs or buying spark plugs, you are welcome to contact our customer service with your vehicle data.
