To carry out the test, the engine must be warm, the battery must be charged, and the spark plugs must be removed.
Order of execution
1. Disable the ignition system by disconnecting the ignition coil high voltage wire from the ignition distributor cap. Ground the wire to the cylinder block.
2. Connect a compression tester to the spark plug hole of cylinder N1.
3. Fully open the throttle and turn the engine over with the starter. After one or two revolutions, the compression pressure should rise to the maximum mark and then stabilize. Write down the result.
4. Carry out a similar test with the remaining cylinders and record the readings.
5. The pressure in all cylinders must be the same. A difference of more than 2 bar between any two cylinders indicates a malfunction. In a healthy engine, pressure should build up quickly. Low pressure on the first stroke, gradually increasing on subsequent strokes, indicates that the piston rings are worn. Low first stroke pressure that does not build up on subsequent strokes indicates a valve leak or blown head gasket. Deposits on the bottom of the valves can also cause low compression.
6. If you have any doubts during the check, contact the experts.
7. If the pressure in any cylinder is too low, carry out the following test to determine the cause. Pour a teaspoon of clean engine oil into the cylinder through the spark plug hole and repeat the pressure test.
8. If after adding oil the compression pressure has increased, then this means that the piston or cylinder is worn. If the pressure does not increase, then the cause is worn or burned valves or a blown cylinder head gasket.
9. Low pressure in two adjacent cylinders almost always means that a head gasket is blown between them.
10. If one of the cylinders has approximately 20% lower pressure than the others and the engine does not idle well, a worn camshaft lobe may be the cause.
11. After completing the check, screw the spark plugs into place and connect the ignition system.
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