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How to Perform a Compression Test on the Engine in a Saturn Ion

    • 1). Warm up the engine in the Saturn Ion before performing the compression test. Testing a cold engine produces inaccurate results. Turn off the engine and disable the ignition system to avoid electrical shock during the test. Remove the four spark plugs from the engine.

    • 2). Choose one of the spark plug holes and insert the compression tester. Crank the starter to rotate the engine and build compression in the cylinder, causing the needle on the gauge to jump. The last number that it jumps to is the compression number for that cylinder. Write it down.

    • 3). Repeat this procedure for each of the spark plug holes, keeping a record of the compression numbers for each of the four cylinders. The numbers should be similar and fall within 10 PSI of each other.

    • 4). Compare the compression numbers to the recommended compression ratio for the Saturn Ion. If the car contains a 2.0L engine, the compression numbers should fall within 15 PSI of 9.5:1. If the car has a 2.2L engine, the ratio changes to 10:1, and if it has a 2.4L engine, the ratio changes again to 10.5:1.

    • 5). Add a small amount of motor oil to any cylinder that has a low compression number and repeat the test to see if the number increases. If it stays the same, the cylinder has worn valves or valve seats, but if it increases, there are worn piston rings or cylinder walls instead.

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