2. Warm up the engine to normal operating temperature. The battery must be fully charged. All spark plugs must be removed. An assistant will be required. If necessary, remove the engine top cover.
3. On engines with an ignition distributor, disable the system by disconnecting the central high voltage wire of the distributor cap and "grounding" it to the cylinder block. Use wire for a secure connection "cigarette lighter". On engines without a distributor, disconnect the wiring from the ignition unit (see chapter 5B).
4. Disconnect the wiring connector from all fuel injectors.
5. Attach a compression tester to the free bore of the first cylinder - a screw-tip compression tester is preferred.
6. Ask the assistant to fully depress the accelerator pedal.
Note. Some later models are equipped with an accelerator pedal position sensor instead of a cable. The throttle will not open until the ignition is turned on.
Turn the engine over with the starter for a few seconds, after two or three engine revolutions, the compression value will increase to the maximum and should then stabilize. Record the highest value obtained.
7. Repeat the measurement on the remaining cylinders, recording the values obtained. Keep the throttle open at all times.
8. Cylinders should show the closest possible compression values. A difference of more than 3 bar between the two cylinders indicates a malfunction. Compression on a serviceable engine should increase quickly. Low compression on the first compression stroke, gradually increasing on subsequent strokes, indicates worn piston rings. A low value on the first stroke that does not rise on subsequent strokes indicates a loose valve seat or a blown head gasket (a crack in the head of the block can also be the cause).
10. Compare the obtained values with the data given in Specifications.
10. If the compression in any cylinder is less than prescribed, carry out the following test to find out the cause. Pour a teaspoon of clean engine oil into the spark plug hole and repeat the compression test.
11. If adding oil will temporarily increase the compression value, this indicates excessive cylinder or piston wear. If the compression does not increase, this indicates a burnt valve, or a burnt head gasket can be blamed.
12. Low compression values in neighboring cylinders are almost always the result of a breakdown of the gasket between the cylinders.
13. If the compression in one cylinder is less than in the other by about 20 percent and the engine is idling "slightly feverish", the cause may be worn camshaft lobes.
14. After completing the check, wrap the spark plugs, connect high voltage wires to them, restore the ignition wiring and install the engine top cover.
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