Why there is no compression in the engine

The engine is the main node in the car and often it does not work at full strength. Problems associated with loss of power of the unit - a common case. Often the cause of unstable operation of the power unit lies in the reduction of compression. If you do not start “technical treatment” in time, the consequences can be serious. Why is there no compression in the engine, how is it measured and what to do when the readings in the cylinders of the power unit are different? Let's try together to understand this issue.


  • 1 Causes of low compression
  • 2 Reliable assistant is a must
  • 3 Measurements - sequence of work
  • 4 Solve the problem
  • 5 Finally

Causes of low compression

why there is no compression in the engine

Coking pistons and rings can cause the disappearance of compression

At the first stage, it is required to find out what could have provoked the occurrence of such a malfunction. Many years of practical experience in operating engines shows that different compression, as well as its absence, can occur under certain circumstances:

  • small metal chips created inside the cylinders during engine operation can cause scratches on the surface of the cylinders and lead to a reduction in compression;
  • burned gasket under the head of the block may cause a cylinder-piston-valve system to leak;
  • a crack in the cylinder block, for example, from engine overheating;
  • valves leakage can be caused by burning, incorrect adjustment (there is no gap between the valve and the camshaft, and the valve cannot close completely) or the formation of carbon / coke on its upper surface;
  • The coking of piston rings can be caused by an untimely replacement of oil or even a design feature of the engine;
  • natural wear of the cylinder surface and an increase in the gap between its surface and the piston;
  • Poor quality fuels and lubricants can also lead to engine coking and premature failure.

Reliable assistant is a must

The device, for measuring indications, is called a compressometer. Available in various variations. It can be used equally effectively for both gasoline and diesel engines. Compressometer is equipped with additional nozzles and adapters, with the help of which they successfully measure on different power units.

engine cylinder compression

Compressometer is used to measure compression in cylinders.

Measurements - sequence of work

For verification, you will need:

  • battery in working condition;
  • candle key;
  • compressometer for measuring and reading.
See also: What is the best motor oil for winter

Before checking you need to start the power unit, because all the work is done on a hot engine. Further:

  • Having muted the engine, we turn out the candles, install a compressor pressure gauge in the candle hole;
  • the assistant in the car, pressing the gas pedal all the way, keeps it in this position from 5 to 10 seconds;
  • we fix the pressure meter readings and repeat the procedure with other cylinders.

Если по завершении проверки результаты существенно разнятся, или engine cylinder compression меньше 10 бар (даже в одном из них), необходимо выяснить причину, по которой возникла проблема. Для этого делаем следующее: заливаем 10 куб. см. моторного масла в цилиндр, проводим замеры. Если показатели, после повторных замеров, остаются на том же уровне, возможно, что всё дело в клапанах. Зажатые регулируем, а прогоревшие клапана заменяем новыми. Если компрессия поднялась, то проблема кроется в изношенности колец.

Fix the problem

compression recovery

You can try to restore compression in the engine by cleaning the valves.

If there is no compression in the engine, the causes of this phenomenon may be different. Naturally, the question arises: is it possible to somehow eliminate the problem? The proposed method does not give 100% confidence. Although in practice it is a very effective method, especially when it comes to the occurrence of rings.

So let's get started. We need fluid to clean the valves. Removing the candles, pour 50 grams into the hole in the cylinder, in which the fault was found. We leave the car alone for 12 hours, after which you need to scroll the power unit to clean the candles, adjust the clearances and, finally, screw the candles into place.

We leave the city. At a speed of 120 km / h we drive 20-30 km. We do a kind of test race. After that we take measurements. If the readings remained at the same level, then the road is the same - to the car service station. The complex of diagnostic works is necessary. Replacement of the cylinder head or overhaul of the power unit is not excluded.

See also: Ways to increase engine power


Care and maintenance of the engine - the necessity and obligation of the owner of the vehicle. The engine must operate smoothly and efficiently in all situations and weather conditions. To do this, it is necessary to conduct a periodic inspection of the power unit, without waiting for the occurrence of failures in its work. Then you can avoid many problems waiting for a motorist on the way.