A compression measurement is normally done to test the engine of racing cars and tuned cars. The measurement can be used to diagnose problems in the engine or to measure and improve engine performance. If you want to learn how to perform a compression measurement, it is useful if you have some basic knowledge about car parts and maintenance.
Steps
Step 1. Bring the engine to operating temperature
This can be done in the following ways.
- If you haven't just driven your car, the engine is probably cold. Start your engine as normal and let the engine run for a few minutes. This way you bring the block to normal operating temperature; but be careful not to overheat the engine from idling for too long. Normally 20 minutes of running is enough.
- Turn off the engine and let the engine cool down if you have just ridden it. If the block is hot, you need to let the engine cool down for about an hour before you can do the compression measurement.
- If you cannot start the car, you can still carry out the measurement. In that case, you won't be able to accurately measure engine performance, but you can still determine if there is a problem with the internal compression if you get a low reading.
Step 2. Turn off the engine completely before starting the measurement
Step 3. Remove the fuel pump relay
By removing the voltage from the fuel pump, you ensure that no fuel is injected into the cylinders.
Step 4. Disconnect the ignition coil electrical connection
In this way, the ignition no longer works, because the ignition coil cannot generate and distribute a spark plug spark.
Step 5. Remove the spark plugs and disconnect the wires from each spark plug
Be careful with the spark plugs, as the ceramic insulation of a spark plug can be damaged or broken.
Step 6. Insert the compression gauge into the spark plug hole of the first cylinder (this is the hole closest to the timing belt)
Do not use any additional tools to tighten the compression gauge, just use your hand to apply pressure.
Step 7. Ask someone to start the engine
The pointer on the meter will rise, when the pointer stops rising, your assistant can turn off the engine. What the gauge now shows is the maximum compression value of the first cylinder.
