2. To obtain accurate test results, the engine must be warm, the battery fully charged, and the spark plugs removed. You will also need the help of another person.
3. Completely turn off the ignition system, for which disconnect the central high-voltage wire from the ignition distributor cover, connect it to ground on the cylinder block.
4. Insert the compression gauge into the spark plug hole of the 1st cylinder. It is preferable to use a meter with a threaded tip.
5. Have an assistant fully depress the throttle pedal and turn on the starter for a few seconds. After the first two revolutions of the crankshaft, the pressure in the gauge should increase to the maximum. Record the maximum meter reading.
6. Repeat measurements for the remaining cylinders, record the meter readings.
7. The compression readings in the cylinders should be almost the same. If the compression difference exceeds the norm, then the engine is faulty. On a healthy engine, the pressure should build up quickly. Low pressure after the first piston stroke and a slow build-up on subsequent compression strokes indicates worn piston rings. If the pressure is low after the first piston stroke and does not increase during subsequent compression strokes, then the cause is a leak in the valves or a leak in the cylinder head gasket (Cracks in the cylinder head may also be the cause). Compression loss can also be caused by carbon deposits on the valve heads.
8. If the pressure in each of the cylinders is at or below the lower limit, inject some engine oil into the cylinder through the spark plug hole (about a full teaspoon), then repeat the test.
9. If, after the introduction of oil into the cylinder, the compression increased, then we can make an unambiguous conclusion that the cylinder walls and pistons are worn out. If the compression increases slightly, or does not increase at all, then the leak is due to burnout of the valves, or a violation of the tightness of the cylinder head gasket.
10. If the compression is equally low in only two adjacent cylinders, then the most likely cause is a burnt gasket between these cylinders. An additional sign is the presence of traces of coolant in the oil.
11. If the compression in one of the cylinders is 20% lower than in the others and the engine is not quite stable at idle, then the cause is wear on the camshaft cam of this cylinder.
12. If the compression value is noticeably higher than normal, then the combustion chamber is covered with carbon deposits. In this case, the cylinder head must be removed and carbon deposits removed.
13. At the end of the measurements, screw in the candles and put the high-voltage wire in place.