Engine diagnosis

Engine diagnosis on modern power plants starts with the same basics that they have always used for testing. It is true that your problems may lie in electronic control parts and high tech systems, but it is always recommended to start with the basics of your engines health When it comes to driveability diagnosis.

This basic engine diagnosis will give you a good indication of the true condition of your engine. Performing a compression test and an engine vacuum test are simple and quick and the cost of the test equipment is also very low. After performing these tests your path to diagnosis will be clearer for any particular problem.

Compression tests

If the combustion chamber leaks, some of the air/fuel mixture will escape when it is compressed, resulting in a loss of power and a waste of fuel. The leaks can be caused by burnt valves, a blown head gasket, worn rings, slipped timing belt or chain, worn valve seats, a cracked head and more.

An engine with poor compression or even low compression will not run correctly and cannot be tuned to factory specifications. If initial engine diagnosis suggests that the cause of the problem may be poor compression, a test should be performed.

A compression gauge is used to check the cylinder compression and is a good indication of the overall health of that particular cylinder. The typical compression gauge indicates pressure in pounds per square inch.

Most compression testers have a vent valve that holds the highest pressure reading on the meter. Opening the valve releases the pressure when the test is completed. The steps for conducting the cylinder compression test are included with the gauges. Specifications can be obtained from a good auto repair manual.

Vacuum testing

Vacuum gauge readings can be interpreted to identify many engine conditions, including the ability of the cylinder to seal, the timing of the opening and closing of the engines valve train, and correct ignition timing. Ideally each cylinder of an engine will produce the same amount of vacuum.

The intensity of the fluctuation indicates the severity of the problem of the leaking cylinder. For example, if the reading on the vacuum gauge fluctuates between 10 and 17 inches of mercury you should look at the rhythm of the needle. If the needle seems to stay at 17 Most of the time, but drops to 10 and quickly rises this reading is probably caused by a problem in one cylinder.

Fluctuating or low readings can indicate many different problems. For example, retarded ignition timing or incorrect valve timing might cause a low steady reading. A burned intake valve might cause a sharp drop in vacuum at regular intervals.

Other conditions that can be revealed by a vacuum test are weak valve springs, faulty PCV, EGR valve operation, compression problems, worn rings or cylinder walls, leaking head gaskets, a manifold vacuum leak, and restricted exhaust systems will also cause low vacuum readings.

Engine diagnosis review

Yes it is true that your engine diagnosis could lead you to a high tech part such as a fuel injector or ignition module. But experienced auto mechanics will most often start with the basics to ensure that the engines overall health is sound before continuing with there engine diagnosis.

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