Engine diagnosis
Engine diagnosis on modern power plants should start with the same basic tests that mechanics have used for decades. It is true that problems could be hiding in electronic control parts and high tech systems. But it is still recommended to start with the basics of engine health first. This basic engine diagnosis tests (explained below) can give you a good indication of the true condition of the engine. Performing a compression test and an engine vacuum test is not to difficult on many model cars and trucks but provides valuable results. Also the cost of the test equipment is low. After performing these tests the path to diagnosis will be clearer for any particular problem. Compression testsThe over head valves close so that this compression procedure can take place at the right time. Both the exhaust and intake valves must seal correctly if maximum compression is to be achieved. The air/fuel mixture gets hotter when compressed. Hot mixtures ignite easier. When ignited it makes more power than the same mixture at lower temperatures. If the combustion chamber leaks, some of the air/fuel mixture will escape when it is compressed, resulting in a loss of power and waste of fuel. The leaks can be caused by burnt valves, blown head gasket, worn rings, slipped timing belt or chain, worn valve seats, 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 cylinder compression and is a good indication of the 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 pressure when the test is completed. The steps for conducting the cylinder compression test are included with the gauges. Specifications can be found in auto repair manuals available online. Vacuum testingMeasuring intake manifold vacuum is another fast and efficient way to diagnose the over all condition of an engine. Manifold vacuum is tested with a specialized vacuum gauge that comes with instructions and different size fittings and adapters.Maybe the most important one is the ability of the cylinder to properly seal. As well as the timing of the opening and closing of the engines valve train, and provide insight about correct ignition timing. Ideally each cylinder of an engine will produce the same amount of vacuum. Therefore, the vacuum gauge readings should be steady and give a reading of about 18-20 inches of mercury. If one or more cylinders produces more or less vacuum the needle of the vacuum gauge will fluctuate.
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 reviewYes 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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