Engine compression test
The engine compression test will bring you back to the basics of engine diagnosis. Sometimes do it yourself Auto mechanics will start looking for the root cause of their problems in high tech automobile systems. In many cases, they will actually find failures in the most basic automotive systems. On this page, we will discuss compression testing procedures. Even if this test does not uncover your problem, it will still give you a great indication of your engines overall health. Why perform a compression test? Internal combustion engines depend on the compression of the air fuel mixture to maximize the power produced by the engine. The upward movement of the piston on the compression stroke will compact the air fuel mixture within the sealed chamber raising the temperature of the charge and making easy to ignite and burn completely. An engine with poor compression or low compression will not run correctly and cannot be tuned properly. If a rough running engine condition is president. This may be considered a symptom that suggests the cause of the problem may be poor compression. A compression gauge is used to check the cylinder sealing capabilities. Engine compression test procedureIt is also recommended to prop open the throttle plate into a wide-open position to allow an unrestricted amount of air to enter the cylinder during the engine test. Mark the spark plug wires and remove all the spark plugs. Connecting a remote starter button to the starter system will allow you to perform the tests on your own instead of having someone crank over the engine for you.
Next Crank the engine over and allow the engine to turn at least four revolutions and then observe and record the reading after the fourth revolution. After you perform this procedure on all cylinders, you can then compare the pressure readings. Note that before you remove the compression gauge from each cylinder, make sure you release the pressure by using the release valve on the tester. Engine compression test low readings
If you have several cylinders or even one cylinder with a low compression reading a wet compression test is then recommended. The procedure performed above is called a dry engine compression test. A wet test is when you squirt a small amount of engine grade oil into the weak cylinders. Reinstall the compression gauge into that cylinder and then conduct the test the same way as above by cranking the engine at lease four revolutions. Document the reading next to your dry compression reading that you recorded earlier. If the reading increases more then 10 psi with the presence of oil in the cylinder the most likely cause of the original low compression reading was a poor piston ring sealing. This may be an indication that the rings are simply worn. And this would be highly likely on an engine with high miles.
Things that can cause low compression are burned valves, a blown head gasket, and worn rings. Also a slipped timing belt or chain that holds the valves open during the compression stroke. And worn valve seats, a cracked cylinder head, or even an engine block crack can also cause compression problems. The engine compression test does not tell you exactly what is wrong with the vehicle, but it does point you in the right direction. This saves you the time of checking items that are not related to the car problem your having.
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Learning about how the engine produces power and converts reciprocal movement to rotational force is recommended. Read my article that explains each cycle in a 4 stroke engine I have lots more free automotive education articles on the subject of engines in cars. This next link takes you from engine compression test to the automotive engines section The you fix cars homepage provides a few highlights of what else is covered on this automobile repair website. This is also a good place to get auto repair advice
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