How to Check Engine Compression Pressure?
3 Answers
Engine compression pressure testing method is as follows: 1. First, ensure the battery is fully charged; warm up the engine to normal operating temperature; 2. Turn off the engine and let it cool for 10 minutes; follow the "Fuel System Safety Inspection Steps" to remove the fuel pump relay. 3. Disconnect the ignition coil connector and remove the spark plugs; 4. Connect a pressure gauge to the spark plug hole of cylinder No. 1, then fully depress the accelerator pedal and start the engine; 5. Start the engine and record the maximum reading on the pressure gauge to obtain the pressure; Additional Information: 1. If the compression pressure increases, it may indicate wear on the piston, piston rings, or cylinder walls, requiring an overhaul; if adjacent cylinders show low pressure, it suggests the cylinder gasket may be damaged or the cylinder head may be deformed, necessitating an overhaul; if the compression pressure remains low, it may indicate stuck valves or poor sealing surface contact, requiring an overhaul. 2. Before measuring engine compression pressure, remove all spark plugs and place the reset-to-zero gauge at the spark plug hole of the cylinder being tested (some compression gauges screw into the spark plug hole). Start the engine and observe and note the value indicated by the gauge's first jump. Release the starter to return the gauge to zero. Repeat the measurement following the same procedure, but each measurement should take the highest value the gauge's first jump can reach as the standard. The value the gauge first jumps to is the true pressure of that cylinder.
Checking engine compression pressure isn't actually difficult. As someone who frequently works on cars, this is my favorite DIY task. You'll need a compression gauge, which can be bought at auto repair shops or online for just a few dozen yuan. The steps are: first open up the engine and remove all the spark plugs, then check each cylinder one by one. Attach the gauge to the spark plug hole, have someone help you crank the engine while keeping the accelerator pedal fully depressed - after a few engine rotations you'll see the pressure reading. The normal range is generally around 150 to 200 psi per cylinder. If one cylinder shows low pressure, it could indicate serious issues like leaking valves, worn piston rings, or a blown head gasket. Remember to wear gloves during testing to avoid burns - safety first! Last time I found a cylinder with low pressure, replacing the seal ring fixed it. Compression loss leads to reduced power and higher fuel consumption, so regular checks can prevent major overhauls. For most accurate results, it's best to perform the test after the car has sat overnight with a cold engine.
Having worked in the workshop for decades, I've handled countless compression pressure issues. The first step is to install a compression gauge into the spark plug hole, and all cylinders must be checked. Be careful not to damage anything when removing the spark plugs, then start the engine and crank it a few times to observe the readings. Standard values vary by vehicle model, but most fall between 150 to 200 psi, with a variance of no more than 10%. Low pressure indicates sealing failure, commonly due to improperly sealing valves or worn piston rings. Before testing, ensure the battery has enough charge to prevent starting failures. Compression pressure is crucial for engine health; insufficient pressure can cause shaking, abnormal noises, or even breakdowns. I advise beginners not to work alone; it's best to have a partner for safety. Fixing this issue sometimes requires just a simple cleaning, but severe cases may need part replacements. Don't forget to record data for each cylinder for comparison, which helps quickly locate the problem.
