How to use an engine compression tester

Is the intake or exhaust manifold in your car producing a loud popping noise? Do you see a dense cloud of blue-gray smoke coming out of the tailpipe of your vehicle? Is your motor vehicle idle too rough? Low engine compression may be the cause of your problem. Learn how to perform a compression test to diagnose the mechanical condition of your car now. This guide will help you to use a petrol engine compression tester.

Step one

Label each of the spark plug wires on your engine, and carefully unplug the wires from their spark plugs. This will make it easier for you to reconnect the wires with their corresponding plugs.

Step two

Unscrew all the spark plugs from the engine as well.

Step three

Remove the air cleaner assembly from the top of the engine so that you have access to the throttle body which allows air to enter the engine through the intake manifold.

Step four

Rotate the throttle wide open by hand, and use a large standard screwdriver to keep it wide open.

Step five

Disable the ignition or fuel system to prevent the engine from starting during the test by removing the ignition coil wire that connects to the distributor or by removing the fuel pump fuse or relay. If you have a motorcar with electronic fuel injection system, disable both the ignition and fuel systems to prevent gasoline from going into the combustion chambers says James E. Duffy in Modern Automotive Technology.

Step six

Connect the hose that is attached to the compression gauge tester to the spark plug hole that is nearest to the front of the engine.

Step seven

Crank the engine just enough so that the needle in the engine compression gauge moves four or six times, and record the gauge reading on a small notepad.

Step eight

Perform an engine compression test on each of the remaining cylinders as you did in step seven until you reach the last cylinder nearest the rear of the engine. Take a note of each cylinder reading on your notepad.

Step nine

Compare your readings to the ones listed on the vehicle service manual for your particular vehicle's make and model. This should reveal to you the mechanical condition of your engine.

Step ten

Reconnect the ignition and fuel system, air cleaner assembly, spark plugs and the spark plug wires.