How to Measure Cylinder Pressure?
2 Answers
Cylinder pressure measurement method: 1. Start the engine to normal operating temperature; 2. Remove all high-voltage wires, loosen all spark plugs by two turns, and crank the starter motor for 6 to 8 seconds or more; 3. Remove all spark plugs, connect the cylinder pressure gauge adapter to the spark plug port, tighten the threaded connection or firmly press the gauge's fire-resistant rubber cone against the spark plug hole; 4. Use the starter to rotate the engine until it completes 4 compression strokes; 5. After reading the gauge measurement, press the relief valve at the cone end of the gauge to release pressure, then measure the cylinder pressure of other cylinders in sequence; 6. Follow the above method to test each cylinder in turn, with each cylinder measured no less than twice, and take the average of the measurement results.
Measuring cylinder pressure is actually quite straightforward, and I've done it myself several times. You'll need a cylinder pressure gauge, which is specifically designed to measure the pressure inside engine cylinders. First, make sure the engine has cooled down—safety comes first. Then locate the spark plugs or ignition coils and carefully remove each cylinder's spark plug. Next, connect the pressure gauge to the cylinder hole via an adapter, ensuring a tight seal to avoid inaccurate readings. There are two ways to take measurements: one is to directly start the engine and let it run for a few seconds—the gauge will automatically display the pressure value; the other is a manual method where you crank the engine and observe the needle movement. I recommend the engine-start method as it better reflects real-world operating conditions. Test each cylinder once and record the values. Ideally, the pressure difference between all cylinders should be within 10%. If one is significantly lower, it might indicate worn piston rings, valves, or other components. After testing, don’t forget to reinstall the spark plugs and check if they’re tightened properly. The first time I did this, I was nervous about making mistakes, so I watched several video tutorials—gradually, I got the hang of it. Remember, regular checks like this can help detect engine issues early and avoid costly overhauls.
