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Safety precautions for changing spark plugs and glow plugs

May 27, 2023

The glow plug is one of the most important components of a diesel engine. In contrast to gasoline and natural gas vehicles, in which the spark plugs are replaced, in diesel vehicles the fuel ignites itself if several conditions are met. However, diesel fuel has a serious disadvantage: it thickens. Once the cold weather sets in, the economic diesel engine stops working – starting with a thick fuel mixture in the system is next to impossible. Glow plugs come to the rescue, regulating the temperature of the mixture.

The system works like this: the glow plug warms up the diesel fuel, which then enters the combustion chamber and, mixing with the air, combusts. In fact, the heating is only required at the start and for another 3 minutes afterward. However, this does not mean that the operation of the plugs is inherently very simple.

There is an average value of the frequency of replacement: most often there are figures in the range of 60-100 thousand kilometers of mileage. But much depends on the manufacturer's recommendations, so do not ignore them. But it is impossible to rely completely on averages, as everyone operates the car differently. Moreover, with the passage of time, the consequences of improper use of the motor are manifested more and more vividly.

Glow plugs come in two types:

● pins;

● ceramic.

They have a similar design, the difference is in the working element. In the pin, the working element is a glow pin made of a thermally corrosive rod, tightly pressed into the body of the candle. Inside it is a sealed magnesium oxide powder and a spiral filament.

The condition of glow plugs should be carefully monitored and changed in time, especially if the car is operated in winter (how often to change will be specified by the manufacturer). Firstly, before winter, it is necessary to check their performance, as even one non-working glow plug will not allow starting the engine at subzero temperatures. If the checkup shows this, it is better to change the whole set, as the rest ones can fail in a short time.

Increased fuel consumption, slow acceleration and trouble starting the engine are the most common consequences of faulty spark plugs.

Changing spark plugs only when they fail is not the right approach. This approach can lead to engine failure. It is important to avoid the onset of spark plug failure. To do this, firstly, it is necessary to follow the recommendations of the manufacturer, which regulates the timing of replacement of plugs. For example, the service life of standard single-electrode spark plugs is up to 30,000 km, while with multi-electrode plugs you can drive 50,000 km before the first replacement.

Troubleshooting spark plugs

Spark plugs and glow plugs fail sooner or later. This can be caused by different reasons – natural aging, use of low-quality fuel and mechanical damage. Let's consider in detail the signs and causes of their failure.

Signs of failure

Let's start with the spark plugs, as the more common ones. So, the signs of their failure include:

● Difficulty in starting the engine (usually accompanied by a long starter);

● the car jerks when driving, poorly gaining speed, it has no traction and power;

● significant increase in fuel consumption;

● decrease in engine dynamics (insufficient revs).

What to do if the spark plug in the engine head is broken and how to unscrew it? Most often the place of the breakage is higher than the threads in the spark plug well.

Some people advise moistening it with a lubricant and try to unscrew the broken spark plug with an extractor and a torque wrench, taking extra care. The wrench must be held steady, constantly monitoring the force applied so as not to twist the threads. If this happens, a costly repair involving the repair or replacement of the cylinder head will be necessary.

Safety precautions for replacing spark plugs

There are no special safety rules for replacing the ignition elements in the car. It is recommended to start it with the engine cooled, so as not to get burned. Since spark plugs work at extremely high temperatures, it is better not to try to replace them immediately after stopping the car, but to wait two to three hours for the engine to finally accept the normal temperature.


Information about glow plug from

How to change spark plugs and wires

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