제목| Engine Compression Test: A Step-by-Step Guide

Conducting a standard engine compression test is a reliable technique to evaluate the condition of your engine’s internal mechanics. This test helps you pinpoint whether the piston rings, valves, and head gasket are working properly. A significant drop in pressure in any cylinder can signal internal degradation that might lead to diminished acceleration, vibration, اتوسرویس داوود or total engine seizure.

In the initial phase, make sure the engine is thermally stabilized. A warm engine gives more accurate results because all parts are at optimal thermal expansion. Kill the engine and disconnect the key and cut power to the fuel pump to prevent fuel from entering the engine during the test. You should also remove the coil packs or spark plug cables to eliminate risk of sudden startup.

Proceed by taking out each spark plug. Note the position of each plug relative to its cylinder so you can put them back in the right spots. Use a specialized spark plug tool and ratchet to gently remove them. Never allow objects to enter the cylinder bores.

Secure the testing device into cylinder one. Make sure it is tightly sealed to obtain reliable data. Have a someone hold the pedal to the floor and engage the ignition for a 6-second interval. Track the pressure reading as it peaks. Note the highest reading. Perform the same test on all remaining cylinders, making sure to reset the gauge between tests.

Following completion of all tests, compare them. A sound powerplant typically has compression from 120 to 170 psi. The readings should be nearly uniform throughout. A variance exceeding 10–15% between the strongest and weakest cylinders may reveal a malfunction. For example, if a single cylinder shows significantly reduced pressure, it could mean a damaged rings, faulty valves, or compromised head gasket.

In the event of a weak compression reading, you can do a wet test to help identify the faulty component. Pour roughly one teaspoon of motor oil into the problematic cylinder’s spark plug port. Then repeat the compression test. If the gauge climbs markedly, the problem is likely damaged piston seals. If the reading stays the same, the issue is probably with the valve seals or cylinder head seal.

Once testing is complete, put the plugs back in, restore the fuel pump and ignition wiring, and run the engine and check for smooth performance. A compression test doesn’t require high-end gear—a simple gauge and common tools, but it gives you deep understanding of internal engine status. Routine checks enable early detection and prevent expensive breakdowns.