Compression Test

If during the operation still have problems that can not be explained by failures in the system of maintenance of the engine, maybe you should check the engine compression. This procedure can often alert you to engine trouble (especially having a great run, respectively, and wear) even before there will be any obvious symptoms, such as: excessive oil consumption, "zakidyvanie" oil spark plugs and so on.). This procedure is performed using the compression tester and its implementation will require an assistant.

Compression test is conducted as follows:

- Warm up the engine to normal operating temperature, make sure the battery is fully charged, then remove the spark plug (see. Section 1);

- Disconnect the central high-voltage wire coming from the ignition coil to the distributor cover and close it on "weight" on the engine block;

- Firmly press or screw Compression (depending on its design, for accurate results it is recommended to use a screw-Compression) to the opening of the first cylinder;

- At this time, your assistant should fully open the throttle and turn the starter motor. After the engine will make several complete rotations, compression pressure should rise to the maximum and to stabilize. Fix the result;

- In the same way, check compression on all other cylinders, each time fixing the result; remember that the throttle when measuring the compression must remain completely open - otherwise you will get incorrect results;

- On completion of inspection replace the spark plugs and high-voltage wire.

Compare the results. The pressures in all cylinders shall have a minimum variation: Permissible pressure difference in any two cylinders in excess of 100 kPa (2 bar), speaks of a mechanical malfunction of the engine. Compression in a serviceable engine should increase rapidly. Low compression at the first engine speed, and then gradually increase in subsequent compression specifies in deterioration of piston rings. Low compression on the first turn and does not increase on the following points to damage to the valves and / or their seats, as it may indicate a broken cylinder head gasket (the reason could also be a crack in the head or cylinder block). Compare results of measurements to the manufacturer. If compression readings in any of the cylinders is too small, then to determine the cause, do the following: a syringe pour a teaspoon of clean engine oil into the cylinder through the spark plug hole, and repeat the test. When pouring oil temporarily improves the compression, it indicates that the pressure drop is cause wear of the cylinder wall or piston rings. Lack further indicates that the cause is a loose fit or burnout valves or cylinder head gasket failure.

The reason for the fall of the compression in two next cylinders is often a breakdown of the cylinder head gasket in between. In this case, it is very likely hit the coolant in the engine oil to form an emulsion. If one of the cylinders of compression is about 20% lower than in the other, and wherein the engine operates slightly uneven, it is likely to cause a deterioration of one of the cams of the camshaft. Excessive compression readings may indicate carbon deposits from the combustion chambers of the engine - Remove the cylinder head and remove carbon deposits.