Updated on 19 October, 2021
A compression test kit is a device that helps determine if your engine is healthy or not. This is especially important because it will tell you if you need to go for major engine repair. The compression test kit tells you if there is unnecessary wear in your engine. The kit can also help you diagnose a problem in your engine if there is any. The test kit is a self-contained unit that is made of plastic tube with a flexible hose that goes into the engine and the compression test is carried out.
The kit includes a digital LED display and a LED thermometer with a digital control switch. The digital control switch allows you to program the readings from the gauge using a graphical menu system. This kit includes a manual that contains detailed instructions on how to read the readings. The reading results are displayed on a LCD screen and they include:
The compression test results usually vary depending on the condition of your engines. The first thing you should do is to compare the reading of your pressure gauge to the data given by the testers. The pressure gauge should give you high readings. If your pressure gauge readings are lower than the testers then you should buy new compressors or oil or other fluids.
The kit carries out a compression testing while the engine is running. The data is usually recorded on a gauge, a graphite black tape, or a large piece of paper. The compression tester measures the compression forces and the pressure at the outlet ports. When the compression pressure reaches about one fourth of the gross vehicle weight, the engine starts to run rough and the engine oil loses viscosity and starts to break down.
Some Compression Test Kit have sensors attached to the fuel injector, carburetor, idle air control valve, electrical ignition system, spark plug, oxygen sensor, battery cables, and solenoid. There are also many other parts like the compression testers themselves, the air filter, the fuel filter, the exhaust system, etc. A good quality test kit should give you good reading if all these components are functioning properly. The testing is usually carried out on a bench top. Sometimes the tester is attached to the engine with a hose. The tester sends signals to a computer where the readings are displayed in a chart.
The first thing you should do when you notice any unusual symptoms with your gasoline engines is to make sure the tester is working properly. If it is broken, replace it. If you find that your test kit has failed and you need a replacement, do not open the cylinder until you get to an auto parts store. The employees there will be able to guide you on what you should do. In most cases, compression testers are made of metal or plastic and they cannot be opened with force.
Another way to test the compression testers is by connecting the hose to a continuity tester or to a lug nut. Pull the hose as far as it will go until you hear a clicking sound. That's the limit of the hose. When you hear this sound, replace the kit and check the other connections.
You will find that most auto parts stores sell compression gauges that have markings on them to indicate the pressure at which the kit was tested. You can consult these for the PSI reading. When you find that the PSI is lower than the marked value, replace the tester so that it gives a true reading. You will probably have to replace the whole kit to get a reading below zero PSI.