How to Fix Low Compression in One Cylinder

The compression in the internal combustion (IC) engine cylinders takes place when air and gas get mixed together. The process is necessary for the car to move and function. If there’s low compression in one cylinder, you will face many problems including misfiring at the time of starting the car or weak engine performance. How to stop this from happening? Well, before you know how to fix low compression in one cylinder, you should have basic ideas about the reasons that cause the problem.

Top 5 Causes of Low Compression in One Cylinder

Understanding the causes of the problem will help you to identify the source of troubles and repair it. Learning these problems will give an insight of how to fix low compression in one cylinder.

Cracked Cylinder Wall

It will trigger poor compression, leading to poor engine performance. To spot the complication, crank the engine with the radiator cap open and watch out if air bubbles coming out. These bubbles are actually gases from the combustion chamber that leak into the cooling system through the cracked wall.

low compression in one cylinder
Crack in the cylinder will leak the gases to the radiator. (photo source:

Gasket Issues

Worn out or misaligned gasket could also be the reason of poor compression. You can use a pressure tester to pinpoint the trouble in this case. It measures the compression level in the cylinder. If the readings are different, you should check the gasket to locate the problematic spot.

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Decrepit Timing Belt

It is the bridge between the camshaft and crankshaft. The camshaft cannot function when the belt breaks or fails. As a result, the intake valve won’t close and the exhaust valve gets sealed. The chain reaction will lead to trapping of the gases inside the combustion chamber and cause the low compression.

Valve Problems

Crank the engine with a compression tester in the place of the spark plug to identify any issues with the valve. Watch out for a gas leakage from either the air inlet manifold or the exhaust pipe. Leakage sound from any of them will confirm that the valve attached to that respective system is faulty.

Worn Pistons or Piston Rings

When these parts are worn out, the gases from the cylinder gets into the engine’s crankcase through them. One way of testing the issue is to pour viscous oil to the spark plug hole so that it reaches the combustion cylinder. If the compression increases, the problem is with the piston or piston rings.

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How to Fix Low Compression in One Cylinder

The first step to repair is to be sure that the compression in one of the engine cylinders is actually low. Use a compression gauge to check the measurement. In case you don’t have one, take the car to an auto servicing shop so that a mechanic can do the testing.

If you find low compression, the next step is to check the cylinder, valves, gasket, and piston as you already know the problem could originate from these areas. If you can detect any crack, damage, or slit, be ready for a costly and lengthy engine repair or replacement job.