How to Use a Compression Tester for Auto Repair How to Use a Compression Tester for Auto Repair

What You'll Need
Owner's manual
Socket wrench
Compression tester
Threaded screw
Cylinder pressure specifications

A compression tester will tell you if the gasoline engine in your car has a cylinder that is not properly sealed. This tester will indicate whether there is a lack of compression in your car engine. There are two different types of compression testers, a screw tester and a rubber-tipped hand-held tester. Both testers will provide the same type of results, however the screw compression tester has been shown to be somewhat more accurate in the readings it provides.

Step 1 – Locating the Proper Pressure Specification

Read your owner's manual to locate the proper pressure specification of your cylinder.

Step 2 – Disconnecting the Spark Plug

Use your socket wrench to disconnect the spark plug from the cylinder to be tested.

Step 3 – Disconnecting the Center Coil Wire

Disconnect the center coil wire from the distributor cap to prevent the engine from starting. This will also enable the engine to turn over in order to test the pressure in the cylinder.

Step 4 – Installing the Compression Tester

Insert the tester into the spark plug opening. Hand tighten the screw on the tester. If you are using a hand held tester, push it into the hole. The rubber tip should be positioned against the spark plug hole threads.

Step 5 – Cranking the Engine

Crank the starter on the engine and observe the pressure reading on the tester. Test the pressure a number of times to get the most accurate pressure reading.

Step 6 – Verifying the Pressure Level

Check the level you found with the one recommended in the owner's manual. If the readings differ, you will need to make some repairs.

Step 7 – Releasing the Cylinder Pressure

Press the release valve on the compression tester in order to release the cylinder pressure.

Got a New Project You're Proud of?

Post it on Your Projects!