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Compression Tester

Diagnose misfires, low power, or starting trouble easily with a compression check. We have top of the line engine compression test kits that let you determine each cylinder’s compression easily to give you a solid picture of your engine’s health.

At its most basic, a compression test will tell you whether or not an engine cylinder has good compression. The second stroke of a four-stroke internal combustion engine is the compressing stroke. This is when the piston compresses air fuel mixture and routes it to the spark plug, precipitating a combustion, when the mixture is ignited by the spark plug to crank the engine. A compression tester measures the condition of your engine’s piston rings, valves, and valve seats. If these components are wearing evenly and the engine is in good condition, each cylinder should have over 100 PSI of compression. Additionally, each cylinder’s reading should be consistent—more than 10% variance between the highest and lowest readings for cylinders should be a red flag.

Once you’ve tested each cylinder, you can learn a lot about your engine. Low compression in one cylinder can indicate a bad exhaust valve. If two adjacent cylinders are low, you could have a blown head gasket. If all the cylinders are low, you might need a new engine because the piston rings and cylinders are likely worn. Higher compression ratios can indicate oil or carbon deposits in the combustion chamber.

Our kits include a compression gauge with rubberized hoses and adapters—everything you need to be a DIY compression tester. You might not know how to check engine compression, but it’s easy to learn. It’s recommended to start with a cold engine, and a disconnected fuel pump and ignition coil. Then, just remove your spark plugs, put the cylinder compression tester adapter in the spark plug hole, and observe the gauge while someone else cranks the engine for a few seconds.

A quick compression test can tell you a lot about your engine’s overall health, and the compression readings give you a good starting point on what needs to be done to get your car back in shape.

Buy compression testers from reliable brands like Actron, Innova, and Mityvac online and get free next day delivery or pick up your tools in an AutoZone near you.