How to Use a Compression Tester?

You might be wondering what is used to reveal the condition of your engine valves; the compression tester does. It not only tests and discloses the state of the engine valves but also its piston rings and valve seats. It also tells if the parts are wearing out uniformly.

A compression test is also necessary as you run it on any engine you are not knowledgeable about. It would be best to keep in mind that a combustion engine consists of four whacks; compression, combustion exhaust, and combustion.

To work correctly, it needs the proper timing of individual components to create a conducive environment for the engine to run appropriately. Each stroke is necessary in the process, and in case your car experiences some problems, there is no way you will take a while before you know.

The compression issues are not typical, and when you incur them, you need to have your car repaired. This is where the compression tester comes as you need it to detect compression issues at an early stage; it will not only save you the cost of repair and time, it also saves the annoyance you will experience on the road.

When something goes amiss in your car, it is due to low compression caused by multiple complications- ranging from wrecked timing belts to blustered head ring or even more other problems. The vehicle may show some signs of low compression like; low climbing hill power, misfire, and at times the car might not start at all.

Low compression might not be the only problem your vehicle is facing, but if you are sure the compression problem is what your car is facing, like having cranky sounds, then a compression tester is what you need.

How to Perform Your Compression Test?

Compression Test

Your engine needs to be warm and not heated up to leave hot bruises on your hands to perform the compression test. Most mechanics let the engine at operating temperature when doing the test. This is uncommon to some engines. You will need protective eyewear and glove to perform the test. Here is what you will need to have at hand;

  • Paper and pen
  • Degreasers and rags
  • Spark plug tools or socket
  • Compression tester
  • Basic mechanical tools
  1. The cold engine detaches the primary wire leading to the ignition coils, and the fuel pump relaxes. This is crucial as sparks and fuel will not muck while in the procedure.
  2. Clean and take note of the sparks’ location and order before you eradicate them- the sparks must be returned in the same order later.
  • Take away the spark plus, be cautious not to destroy the ends.
  1. Take your time and observe each tool for any clues why the combustion chamber has problems.
  2. Note down the number of each cylinder. If the numbers have a slight difference, it is said to be expected. In case the numbers are far most different from each other, have a qualified mechanic check your engine. It would be best if you did the compression tests at cranking engine speed. Leave your gauge for ten seconds to get the right combustion pressure of the cylinder.
  3. Once you are done with the testing, please take out the compression tester by loosening it from the cylinder.
  • Go ahead and attach the sparkplug into the cylinder gently after checking for any damages.
  • Mount the plug wire in its rightful place. Push it definitely on the sparkplug terminal- all this while testing the cylinder manner. They should be on the 5% level of each other.

What the results mean

There is more than just one thought you get after doing a compression test. For an average engine that offers you better performance, it should have a compression of 135 PSI. If the reduction goes to an average of 85 PSI, it means there is a bigger problem in your car worth repair.

The compression testing results should not be more than 135 PSI, and if the cylinders have uneven compression readings, it should not go beyond 20% between the highest and lowest. Differences between the cylinders show a leaky, broken, or worn-out valves- it can also be both.

During engine cranking, observe your tester, you should notice the differences of each cylinder pump. The cylinder produces 40 PSI in the first laps while it has 35 PSI in the continuous stroke.

Problems incurred by cylinders may cause inadequate pumping due to bad rings or excess oil. Some other issues to be incurred when doing a compression test are;

  • temperature
  • cranking speed
  • altitude
  • high-performance profile camshaft.
  • worn camshaft lobes

Your compression tester tells you how much wear your engine got. It also informs you of the state of your cylinder and when you need a repair. You can also take a precaution for your low compression cylinder, take a little amount of engine oil, put it in the cylinder, then go ahead and do a compression retest.

When testing for less, here is what you need to do; start by taking off the cylinder, be careful in this and go through the manufacturer’s manual to know how the cylinders are numbered and arranged. Attach the compression adapter to the car’s spark plug hole. Many compression testers come handy with three or more pieces, in this case, cord all the parts together with your hands starting from the position near the engine out.

The next step is to crank your engine for five seconds while you check the tester. Several vehicles have a psi of around 125 to 165. Take note of the number, take off the gauge, and repeat every cylinder’s testing process. If a cylinder has a fallen number of psi from the others, then the car problem emanates from that specific cylinder. But if the problem comes from all the cylinders, the problem might be a mechanical upheaval or your timing chain.

What the results to Use a Compression Tester

The compression test is usually low during the first rap and continues building up as the strokes continue. It does not reach its regular, and on adding some oil, compression increases. When you add oil to improve the compression and nothing happens, then the problem is not in the cylinders but due to broken head gasket, which causes leakages between the car cylinders.

What to know about Compression Testing?


It is a basic test to know the amount of leakage between the valves and the piston ring in the cylinder. The compression test done in the standard vehicles is different from the compression test done to the aircraft engine. There are two types of compression testing; the direct compression test and the differential test.

Differential Compression Testing

It is a convenient method to do compression testing of engines. When conducting the test, you have to use two testers to gauge the engine pressure. In the process, the air is compressed to the regulator gauge, the air then moves to the calibrator restrictor into the cylinder pressure gauge. The cylinder indicator is to indicate pressure and any pressure loss will be displayed in the pressure gauge being less than the regulator gauge.

Direct Compression Testing

In this testing process, the compression tester is installed in the spark plug; the engine turned over while determining the cylinder’s built-up pressure. With this type of compression testing, be sure to get different results depending on the reliable varieties.

The compression tester is a crucial element in differential compression testing; it ensures the test’s accuracy is carried out. Nevertheless, the tester needs to have some specific things to offer the best compression testing results;

  • dead-end check

for the tester to accurately be used in doing a compression test, it needs a dead end. By capping off the tester’s end, you ensure the cylinder’s stabilization and the regulator pressure gauge give the same pressure results. any slight difference from the two indicates defective meter or a leakage in the tester

  • valves

The tester needs to have valves to be mounted between the cylinder gauges. When performing a check, the valve should be closed, having in mind this area being another source of leaks. In that, the tester valves should be gotten rid of before the gauge starts leaking

  • storage

another vital factor to consider in getting the right results in a compression test is your tester’s storage. Dirt is the biggest enemy of your tester that can lead to the tester giving you inaccurate results. Make sure you find a clean and safe place to store your tester each time you finish your compression testing. The tester a crucial tool that needs a proper handle.

  • proper outlet

the last thing to know about your tester; it needs to have adequate orifice to conduct appropriate compression testing to your engine. You should get a specified tester with an orifice dimension matching a particular engine for additional compression testing.

If the problems look more complicated to detect with the compression tester, visit your nearby mechanical shop and get diagnosed with further issues. Do not continue driving your car while it has low compression; it will cause you harm, or the problem might end up being worse.



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