Compression test
Note: This operation will require a specialized diesel compression tester.
1. In the event of deterioration in engine performance or in the event of ignition failures, the cause of which cannot be attributed to the ignition system or fuel system, the compression test is a means of diagnosing the condition of the engine. Carrying out this check regularly helps prevent serious malfunctions.
2. Since the operating pressures in a diesel engine are much higher than in gasoline engines, a specialized diesel compression tester will be required. The compression tester is attached to an adapter that is screwed into a threaded hole instead of a nozzle or glow plug. If such a device is not available, contact the workshop where this compression tester is available.
3. If there are no special remarks in the instructions for use of the compression tester, pay attention to the following:
- A) The battery must be in working condition, the air filter is clean, the engine must be warmed up to operating temperature.
- b) All injectors or glow plugs must be removed prior to testing. If the injectors are removed, remove the flame arresters so that they do not shoot when the engine is cranked.
- V) The fuel metering control shut-off solenoid valve must be turned off so that the engine does not accidentally start and fuel is not sprayed in all directions.
Note: Since the wiring will be disconnected, fault codes will be stored in the memory, which must be cleared after the compression test.
4. Since the diesel engine does not have a throttle, it is not necessary to press the accelerator pedal to the floor.
5. Manufacturers prescribe a wear limit - minimum compression values \u200b\u200bare written in Specifications. If, after checking the compression, there is doubt about the correctness of the measurements, seek advice from diesel specialists or an Audi dealer.
6. The cause of low compression in a diesel engine is more difficult to determine than in a gasoline engine. If oil is poured into the combustion chamber ("wet" verification), it will spread inside her (the chamber is located in the bottom of the piston) and will not seal the piston-cylinder gap. Be that as it may, the following information can be used to make a rough diagnosis.
7. Cylinders should show the closest possible compression values. A difference of more than 5 bar between the two cylinders indicates a malfunction. Compression on a serviceable engine should increase quickly. Low compression during the first compression stroke, increasing gradually during 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).
8. Low compression values in neighboring cylinders are almost always the result of a breakdown of the gasket between the cylinders.
Air Leak Test
9. The air leak test measures the amount at which compressed air leaves the cylinder. This test is an alternative to a compression test and is more useful in many cases as the escaping air points to a leak (rings, valves or head gasket).
10. To carry out such a check, you need specialized equipment that is not available to a motorist. If a loss of compression is suspected, have it checked by a suitably equipped workshop.
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