Compression pressure test

Checking the condition of the engine can be done by measuring the compression pressure in the cylinders. If this check is carried out regularly, it is possible to know in advance the beginning of engine wear, without waiting for the moment when wear manifests itself in low engine efficiency.

1. Warm up the engine to operating temperature with the battery fully charged. Unscrew the spark plugs.

2. Remove the connectors from the fuel injectors of the fuel injection system.



3. Install a compression tester in the hole of the candle of the first cylinder.

4. The assistant should press the accelerator pedal to the stop and turn the engine with the starter. After turning the crankshaft one or two revolutions, the compression pressure should increase to a maximum and then stabilize. Record your maximum score.

5. Check the rest of the cylinders in the same way.

The compression pressure in all cylinders should not differ by more than two units. Note that the amount of compression should increase rapidly on a healthy engine; low compression pressure on the first revolution of the crankshaft followed by a gradual increase in pressure on subsequent revolutions of the crankshaft indicates worn piston rings. A low pressure value at the first revolution of the crankshaft, which increases slightly thereafter, indicates a valve leak, a blown cylinder head gasket, or a crack in the cylinder head. Worn valve stem ends can also result in low compression pressure.


Opel does not determine the exact compression pressure, however, if the compression pressure in the cylinders is less than 10, then this indicates engine wear.

If the pressure in one cylinder is low, then carry out the following test. Pour some engine oil through the spark plug hole into the cylinder and check the compression pressure.

If adding oil to the cylinder increases the compression pressure, this indicates that the cylinder or piston rings are worn.

Low pressure in two adjacent cylinders indicates a burnt gasket between the cylinders.

If the pressure in one cylinder is less than 20% than in the others and the engine runs erratically at idle, this indicates a worn camshaft cam.

If the compression pressure is too high, this indicates that the combustion chamber is covered with a thick layer of soot.

After this check, screw in the spark plugs and connect the high voltage wires to them.