All gasoline engines have spark plugs. These parts ignite the air/fuel combination inside the motor and last a long time. The following article will teach you how to test spark plugs in car or your truck with ease.
However, age, use, and poor fuel quality affect the work of safety plugs. Therefore, they need replacing over time.
If you can’t start your vehicle or have a hard time starting your car, perhaps a bad spark plug needs replacing. You can test your spark plugs and see if they perform properly or need changing.
In today’s article, we will share ways you can test spark plugs and safety tips. The process takes minutes and costs little or nothing, so let’s dive right in!
Contents
Safety First!
The ways you can test spark plugs in your car include a multimeter and other tools, but some also require working with exposed wires under the hood. So, here’s a list of safety tips you must remember and practice before testing spark plugs.
Protect Yourself
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Testing and replacing spark plugs isn’t dangerous, but you should use protective gloves and glasses just in case something goes wrong.
Let the Engine Cool Off
Never pull spark plugs when the engine’s hot or running because many parts under the hood can harm you, including spark plugs in poor condition.
So, let the engine cool off before testing and replacing these parts. Moreover, steer clear of any moving components during the testing process.
Don’t Touch the Spark Plugs During Testing
When the ignition’s engaged, avoid touching the spark plugs.
The low amperage won’t harm you. However, spark plugs carry about 20,000 volts. So, you won’t have a pleasant experience.
How To Test Spark Plugs in Car: 5 Different Methods
Any gas-powered engine has spark plugs. These parts need occasional inspection and testing, and here’s how you can test spark plugs properly in different ways.
Method 1: Disconnecting Each Spark Wire With a Running Engine
The first method doesn’t require any tools, but you should wear gloves for safety.
First, you should start your car and let the engine run. Then, disconnect each spark plug wire one by one.
If you remove a specific spark plug wire and the speed of your engine drops or you hear your engine running rough, that’s a sign of a spark plug in good condition.
However, if you remove a spark plug wire and don’t notice any changes in your engine’s performance, that’s a sign of its bad condition.
Test each of them in the same manner and replace the faulty ones.
If you don’t have a multimeter, you can quickly and easily test your spark plugs and find faulty ones.
Method 2: Conducting a Spark Plug Ignition Test
You can also conduct a spark plug ignition test with a screwdriver.
Carefully remove the spark plug wire, import a screwdriver into it, and place the end on a metal surface.
A spark plug in good condition will give off a spark or make a crackling sound.
The signals say the voltage links to the tested spark plug through the wire. So, test your spark plugs and their wires the same way and replace faulty ones.
Method 3: Using a Spark Plug Tester
You can test your spark plugs with a spark plug tester and find bad ones. You can buy a good tester at your local auto parts shops.
Once you purchase this tool, turn off your vehicle’s engine, remove the key, and shut off the battery’s negative terminal before testing the spark plugs. Then, find the spark plugs and draw the boot on the first.
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Push the spark plug tester’s boot on the spark plug and connect the standard spark plug boot to the spark tester.
Attach the spark plug wire to the tester’s other end and reconnect the battery’s negative terminal. Have someone start your car while you observe the spark plug tester.
If your spark plug doesn’t need replacing, you will see the light flashing rapidly. If there’s no flash, it needs changing.
These testers don’t cost much and enhance DIY tasks. Therefore, we suggest buying one, especially if you regularly check your spark plugs at home.
Can You Build a Spark Plug Tester at Home?
If you don’t own a spark plug tester and are on a budget, don’t worry. You can create one at home and check spark plugs with common materials.
Here’s how:
- Obtain a standard spark plug wire, a short screw with round edges on one point, and a see-through tube.
- Cut the spark plug wire in half.
- Cut a small piece of the see-through tube.
- Attach the piece at both ends of the wire you’ve just cut in half.
- The tube should become the connecting link between the ends of the wire.
- Leave a small space (a half inch) between the 2 pieces of spark plug wires.
- Add the screw to one of the tips of the spark plug wire.
- Connect the side of your homemade tester with the screw to your vehicle’s spark wire boot and the other end to the spark plug.
- Have someone start your car while you watch the tube between the 2 pieces of spark plug wire for a rapid flashlight.
- If there’s a rapid flashlight, you have a good spark plug.
- If there’s no flashlight, it needs replacing.
- Repeat the same with each spark plug and ensure they all function properly.
Method 4: Grounding Test
First, stop the fuel supply for the engine.
If you have a fuel-injected car, pull the fuse for the fuel pump. If it’s a carbureted engine, disconnect the plumbing to the fuel pump.
Afterward, run the engine until all fuel in the system burns off.
- Take off the spark plug wire or coil pack.
- Take off the spark plug from the cylinder head.
- Connect one spark plug to plug the wire or coil pack.
- Put it on a grounded metal surface.
- Start the ignition or have someone start it.
- Watch for spark.
- You should get a strong blue spark.
- You need a new spark plug if you get a dull and weak orange spark.
- If there’s no spark, connect a new one and repeat the test.
- If you get a spark, you know the previous one needs replacing.
- If you don’t get a spark with the new one, you can check other ignition system parts, such as the combustion chamber, engine block, etc.
- Use a multimeter for sure results.
Method 5: Testing Spark Plugs With a Multimeter
If you have a multimeter at home, you will save time because testing spark plugs with a tool like this isn’t time-consuming.
On the contrary, it’s a time-saving and versatile tool for testing electrical resistance.
If it’s your first time using a multimeter, don’t worry. Here’s a list of steps you can follow and use this tool properly:
- Connect the black and red probes to the device.
- Set the device to “ohms.”
- Touch the test leads together (the device should say 0 ohms).
- Separate the test leads (the device should display infinite).
- Remove the ignition wire and unscrew the spark plug you will test.
- Adjust the resistance to about 20K ohms.
- Add the black probe from the device to the spark plug’s terminal. Then, apply the red probe on the center electrode at the tip.
- Carefully connect the probes.
- Observe the device.
- You should get a resistance of between 4K and 8K ohms.
How Many Ohms Should a Spark Plug Have?
Most spark plugs for regular vehicles have between 4K and 8K ohms.
How Can You Check for Faulty Spark Plug Wires?
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You can quickly determine faulty spark plug wires by taking a closer look at each. Signs of rot or wear mean you should replace these components.
However, we suggest testing the electrical resistance with a multimeter for sure results.
Can a Spark Plug Shock Kill You?
In short, you won’t die out of a spark plug shock unless you have a heart condition. You will only feel a little pain.
Spark plugs receive energy with high voltage and low amps. So, you can’t get seriously hurt by a spark plug shock.
Conclusion
You can test spark plugs in your car using different methods. Some methods require the removal of the compartments, while others don’t because looking at the spark plugs can reveal their condition.
For example, if you compare old with new spark plugs, you will see a clear difference in the tip. If your old ones have worn-out tips, you should install new ones.
They also need changing if there’s fuel or oil contamination.
Use a multimeter if there’s no visible damage, but you suspect a malfunction. This handy tool can help determine the condition of spark plugs, as described above.
Hopefully, the methods in this article can help you test your spark plugs properly so that you can change any if it’s faulty or malfunctioning.