This is a simple mechanical engineering project which can be executed at low cost.
A Spark plug tester essentially consists of a metallic portion followed by something that looks almost similar to a Spark Plug and a connecting port in a tubular arrangement.
What does the tester do?
The Spark plug tester performs the following functions to check the proper working of the Spark plug.
1. Checks if the Spark plug is accepting current from the wires that go to the spark plug.
2. Proper firing of the Spark plug
The main idea of using a spark plug tester is to avoid the removal of the spark plug and testing it. This leads to saving valuable time.
How does it perform the above functions?
a) Testing the wires:
At first, disconnect the wires from the spark plug which you wish to test. Place the wire to the end of the tester. The tester is then clamped to the engine block. This grounds the unit and allows the flow of charge through it. With that done, you should fire up the engine and keep an eye on the end of the spark plug tester for sparks. If sparks are visible, then the wires are working fine.
b) Testing the Spark plug firing:
The long end of the spark plug tester is inserted onto the spark plug. The other end of the spark plug tester is plugged into the boot on the spark plug wire. Fire up the engine and look for spark in the window of the tester.
Testing the spark plug is simple but you should make sure it is done the right way so as to not hurt yourself in the process.