Compression check (Opel Frontera B)

The condition of the engine can be checked by measuring the compression in the cylinders. If this check is carried out regularly, it is possible to know in advance the onset of engine wear, without waiting for the moment when wear manifests itself in low engine efficiency. Based on the results of the inspection, it is possible to judge the condition of the valves or pistons (piston rings), and also whether the engine has exhausted its service life and is subject to replacement or major repairs.

To check the compression, you need a compression tester with a rubber cone tip with a measurement range of up to 40 bar.

The engine must be warmed up to a temperature of 80°C and the battery fully charged.

Remove the ignition coil block cover, disconnect the high-voltage wires from the spark plugs and use the special KM-194-E tool to unscrew the spark plugs. Disconnect the wiring harness connector from the ignition control unit, thereby disabling the ignition system. Remove the fuel pump relay.

Insert the tip of the compression tester into the spark plug hole of the first cylinder.

The assistant must press the accelerator pedal all the way down (i.e. fully open the throttle valve) and turn the engine crankshaft with the starter for 4 seconds, while the engine crankshaft speed should be at least 300 min⁻¹. Write down the result obtained.

Note: When checking compression, do not stand in front of the spark plug holes, as when the crankshaft is turned by the starter, engine oil and fuel may be ejected from the cylinders through the spark plug holes.

There should be approximately equal pressure in all cylinders. A difference of more than 1 bar between any two cylinders indicates a fault.

Note that the compression value should increase rapidly on a healthy engine: low compression on the first crankshaft revolution, followed by a gradual increase on subsequent crankshaft revolutions, indicates wear of the piston rings. A low compression value on the first revolution of the crankshaft, which increases slightly later, indicates a loose valve fit, a broken cylinder head gasket, or a crack in the cylinder head. Carbon deposits on the backs of the valves can also cause low compression.

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

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If pouring oil into the cylinder increases compression, this indicates that the cylinder or piston rings are worn out. The lack of an increase in compression indicates that there may be a leak through burnt valves or a blown head gasket.

Low pressure in two adjacent cylinders indicates a burnt-out gasket between the cylinders, and engine oil should appear in the coolant.

If the pressure in one of the cylinders is 20% lower than in the other cylinders and the engine runs unsteadily at idle, then the camshaft cam is worn out.

If the compression pressure is too high, this indicates that the combustion chamber is covered with a thick layer of carbon deposits. In this case, it is necessary to remove the cylinder head and remove the carbon deposits.



After checking, screw in the spark plugs, tighten them to a torque of 25 N·m, connect the high-voltage wires to them and restore the functioning of the ignition system.

Install the ignition coil cover onto the cylinder head cover and secure with bolts, tightening them to a torque of 3 Nm.