Compression tests are done during racing to test the engines of racing cars and other vehicles with high performance engines. This test is useful for detecting engine problems or for measuring and improving performance. It is helpful to have basic automotive knowledge to learn how to do a compression test.
Steps
Step 1. Bring the engine to normal temperature
You can do this in the following ways.
- If you haven't driven your car recently, the engine will be cold. Start the vehicle and leave it on for a few minutes. This will warm the engine to normal temperature, however you must be careful not to overheat it too much by keeping it running for too long. It is sufficient to keep the engine running for 20 minutes.
- Turn off the engine and let it cool down if you have used your car recently. If the engine is warm, leave it off for at least 1 hour before doing a compression test.
- If you cannot start the vehicle's engine, continue with the test directly. While you won't be able to thoroughly test the engine, it will tell if there are internal compression issues if you get a low result.
Step 2. Turn off the engine completely before starting
Step 3. Remove the fuel pump
Thus the fuel will no longer reach the cylinders.
Step 4. Disconnect the ignition coil electrical connections
You will disable the starting system as the coil will not be able to create and distribute current to the spark plugs.
Step 5. Remove the spark plugs and disconnect the wires from each
Use great caution with spark plugs to avoid damaging the ceramic insulating coating and end up with defective spark plugs.
Step 6. Put the pressure gauge inside the spark plug hole of the first cylinder (the hole near the belt)
Do not use tools to squeeze the pressure gauge, just use your hands.
Step 7. Ask someone to start the engine
The needle in the gauge will reach its maximum value, when this happens ask whoever helps you to turn off the engine. The maximum value is the maximum compression of the first cylinder tested.
