How To Test Spark Plug Wires properly

A spark plug wire is a wire that is installed from the distributor or coil to the spark plug. The spark plug wire flows the high voltage electricity the ignition coil generates. Spark plug wires are commonly used in older cars with a gasoline engine that still uses the old model carburettor and EFI systems and uses an integrated distributor or igniter.

Why do spark plug wires need to be tested? Basically, spark plug wires can also be damaged like other car components, so we must check them if needed. Usually, checking the spark plug wires is done when the engine has a problem. Here are some problems that occur when the spark plug wire is problematic.

Engine vibrating at idling rpm.
When accelerating, the engine vibrates strongly and lacks power.
There is noise on the car radio.
Failed emission test due to too high hydrocarbon emission

This article will share tips on testing a complete car spark plug wires. How to? Check out how to check the spark plug wires below.

I. Test for electrical leakage of spark plug wires visually

The main function of the spark plug wire is to conduct electricity generated by the ignition coil to the spark plug. The electric current flowing in the spark plug wire has a very high voltage. If there is an electrical leakage from the spark plug wire (the wire insulator at the spark plug head is leaking, the wire is peeling or cracked), then the damaged part can emerge as an electric arc (electrical jump) from the spark plug wire to the nearest ground.

Therefore, this test should be carried out before visually inspecting the spark plug wires and checking the resistance value with a multimeter. There are several ways you can do to test the car's spark plug wires for leakage currents, such as:

1. By removing the spark plug wires one by one when the engine is running

This method is the easiest and cheapest way. Here's how:

Turn on the engine and leave it in the idling rpm position
Disconnect the number 1 spark plug wire from the spark plug and hold it at a distance of about 3-5cm from the spark plug head
Look visually at the end of the spark plug wire head. If an electric arc comes out instead of the head end of the spark plug wire, then the spark plug wire is leaking and damaged.
Put the spark plug wire back into the spark plug and do steps b to c above for the other spark plug wires.

Note: When the spark plug wire is removed from the spark plug, the engine will usually limp. It is normal because the spark plug we unplugged will not work, causing the engine to limp due to the absence of combustion in the spark plug cylinder that we removed.

2. By using a water sprayer

The second way to check for spark plug leaks is to use a water sprayer (a water spray that produces water mist, for example, in a sprayer for ironing clothes). Here's how to check spark plug wires with a water sprayer.

Turn on the car engine and leave it at the idling rpm position
Spray water with a sprayer onto the spark plug wires in sequence. Start with spark plug wire no.1
After the spark plug wires are sprayed with a water sprayer, pay attention to the spark plug wires. If an electric arc comes out of the spark plug wires, it means the spark plug wires have leaked.
Spray all the existing spark plug wires sequentially.

Note: Spray water on the spark plug wire while paying attention to whether there is an electric current leak or not. The engine usually becomes limp (shake) when there is a leakage current.

3. With an insulated iron (screwdriver) connected to the ground body

The last way to check for leakage of spark plug wire current is to use an insulated iron connected to the ground body. Here's how.

Turn on the car engine and leave it at the idling rpm position.
Attach the end of the checking tool wire to the ground body or negative battery.
Bring the iron closer to the spark plug wire and gently slide it from one end to the other along the spark plug wire.
If there is an electric arc coming out of the spark plug wire, it means the spark plug wire is leaking.
Do the same for the other spark plug wires

Note: Make sure the insulator of the tool to check is perfect. Otherwise, it can cause you to be electrocuted from the spark plug wire.

II. Visual inspection of spark plug wires

After checking the leakage current on the spark plug wires, the next step is to inspect the spark plug wires visually and physically. Here's how.

Remove the number 1 spark plug wire from the distributor and the spark plug.
Pay attention to the head end of the spark plug wire, the spark plug wire insulator and the end of the spark plug wire.
Make sure the rubber and insulator are in good condition, still elastic, not cracked and not torn.
If the rubber and insulator on the spark plug wires are cracked, this can create an invisible current leak. It's a good idea to replace it if a crack occurs.
Also, ensure the spark plug head terminals inside the spark plug wire heads are not covered in a green powder, are not broken, and are in good condition.
Check in the same way for the other spark plug wires.

Note: Check the spark plug wires one by one. Remove one-test-install again, then remove the next spark plug wire. It is so that you do not install the wrong position and order of the spark plug wires. Installing the wrong spark plug wire arrangement can cause an explosion due to incorrect ignition.

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III. Test the wire resistance value using a multimeter

The last thing that needs to be done to test the car's spark plug wires is to check the resistance value of the spark plug wires using a multimeter. Checking the resistance value of this wire requires a multimeter (ohm meter) as a tool. Here's how to check spark plug wires with a multimeter.

Prepare a multimeter for resistance measurement (ohm meter), and do a "zero adjustment" to ensure the correct measurement value.
Remove the spark plug wire no.1
Measure the resistance value of the spark plug wire by attaching the + probe to one end of the spark plug wire and the probe - to the other end.
Record the measured resistance value and replace the #1 spark plug wire with its original position.
A good spark plug wire has a resistance value of 16 KΩ/m (kilo-ohms per meter). If the length of the spark plug wire is less than 1 meter, then the value will be less than 16 KΩ/m. For example, if the spark plug wire length is 50 cm, a good resistance value is 8KΩ.
Take measurements for the other spark plug wires.

By doing the three steps on how to test spark plug wires as above, we can ensure that the spark plug wires are still good or have been damaged.