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How To Test Spark Plug With Multimeter


Testing spark plugs with a multimeter is an easy way to know if they need replacing. Spark plugs are important for your car’s ignition system. Regularly testing them with a multimeter can make sure that everything runs smoothly. Here’s how:

  1. Gather materials: You’ll need things like a spark plug, socket wrench or ratchet tool, torque wrench or torque meter, insulated lead wire set, safety gloves, and eye protection.
  2. Prepare the area: Have a clear workspace with no dirt or grime.
  3. Unscrew old spark plug: Use the removal tool for your car model (socket wrench or ratchet tool).
    • Disconnect electrical connection: When unscrewing, disconnect the electrical connection on the #4 lead wire.
  4. Test continuity: Use an appropriate digital array. Connect the negative lead from Clip A to the chassis ground source/frame. Connect the positive lead from Clip B to the central terminal on the Ignition Coil. Connect terminals 1 & 2 to the electrode & center insulator on the Spark Plug being tested.

Gather the necessary materials

To test your spark plug with a multimeter, you will need some materials and tools. Get a digital multimeter, spark plug socket, extensions, ratchet and spark plug wire. Having the proper tools is essential for an easier and more accurate testing process.

The first step is to have the necessary materials available:

  • Digital multimeter
  • Spark plug socket
  • Extensions
  • Ratchet
  • Spark plug wire

Spark plug

To keep your car running smoothly and increase fuel efficiency, it is important to replace your spark plug at regular intervals. Before replacing the spark plug, you need some materials.

Here’s a list:

  • Socket wrench and socket set
  • Eye protection, gloves and face shield
  • Anti-seize lubricant
  • Spark plug gap gauge
  • Thermal paste or grease
  • Spark plugs
  • Distributor cap
  • Gap adjustment tool (if needed)


To test a spark plug (also known as an ignition coil), you need a multimeter. Multimeters measure current, resistance and voltage. Plus, get insulated hand tools like pliers and wire strippers, an adjustable wrench, safety glasses, and rubber gloves. Wear safety goggles for eye protection when handling or testing spark plug components.

You’ll need conducting grease or paste for good electrical connections. Finally, have the spark plug, gasket and boot ready for testing:

  • Spark plug
  • Gasket
  • Boot

Prepare the spark plug

To test a spark plug with a multimeter, prep is a must! Clean the electrodes, set the gap, and attach the plug to the multimeter properly. This is necessary for accurate results.

Let’s take a look at the steps needed:

  1. Clean the electrodes.
  2. Set the gap.
  3. Attach the plug to the multimeter properly.

Remove the spark plug

Before you start testing the spark plug with a multimeter, make sure it is installed correctly in the engine. If you don’t have a spark plug wrench, use an adjustable wrench/socket and ratchet. Twist and pull back while pulling straight out to keep debris away.

Once the spark plug is removed from the cylinder head, you can test it with the multimeter.

Clean the spark plug

Before troubleshooting or replacing a spark plug, it is important to make sure it is clean. Motor oil and dirt can accumulate over time, blocking it from sparking correctly. Inspect the plug for physical damage before cleaning. If any cracks or damage are found, replace the spark plug.

Be delicate when handling the spark plug. Gather materials such as a wire brush, paper towels, solvent cleaner and WD-40. Tilt the wire brush towards the center column on top of the plug. Brush counterclockwise until all carbon deposits are gone. Then lubricate the spark plug before reassembling.

Test the spark plug

Need to test a spark plug? Here’s how! Gather up a set of insulated pliers, a spark plug wrench, a clean rag, and a multimeter. Now, you are ready to check the spark plug’s condition. Follow these steps and learn more:

  1. Disconnect the spark plug from the spark plug wire.
  2. Clean the spark plug with the rag.
  3. Set the multimeter to the resistance setting.
  4. Place the multimeter probes on the spark plug terminals.
  5. Compare the resistance reading with the manufacturer’s specifications.
  6. If the reading is not within the specified range, replace the spark plug.

Set the multimeter to the correct settings

To test a spark plug, the multimeter must be set to the correct settings. The most common settings are DC Volt or Ohms and AC Voltage.

  • For DC Volt, choose a range higher than expected. Put the selector on DCV. This works for Ohms resistance measurements too.
  • For AC Voltage, select an appropriate range. Place the selector on ACV for Alternating Current Voltage measurements.

Before you proceed to other steps, read the user manual and adhere to safety regulations. Make sure to ground the spark plug correctly. Adjust if needed.

Connect the multimeter to the spark plug

Turn off the engine. Disconnect the wire from the spark plug but keep it connected to the distributor.

Attach the positive lead of your multimeter to the terminal of the spark plug. Attach its negative lead to a good ground on the engine block or head. Ensure both connections are secure. Turn on your multimeter. Set it to measure ohms or resistance. Look for a reading between 4 and 10 ohms. Any reading outside this range requires further investigation.

Read the results

Inspect a spark plug to see if your engine is running correctly. Look for a porcelain insulator on the plug’s center electrode. It should be even and clean. Check the electrodes for burning or damage, as it could be caused by an internal combustion issue or bad spark timing.

Look for deposits on the insulator tip and electrodes. This may mean the air/fuel mixture is off or something is building up in the engine. Check the color of the electrode core; black could mean bad fuel pressure or quality. Finally, make sure there’s no oil around the base of the spark plug; this could mean oil is leaking past your valves or piston rings.


Test your spark plug with a multimeter. This will save you time and money. Get the right equipment. Once you practice, you can do it quickly. If you have any doubts, consult an automotive professional. Then make repairs or adjustments. Your vehicle will be ready for the road.

Frequently Asked Questions

Q1: What is a spark plug?

A1: A spark plug is a device used to ignite the air-fuel mixture inside an internal combustion engine by providing an electric spark.

Q2: How do I test a spark plug with a multimeter?

A2: To use a multimeter to test a spark plug, first ensure the spark plug is connected to the engine and turn off the engine. Then, set the multimeter to the ohms setting, touch the multimeter leads to the spark plug terminals and observe the resulting reading.

Q3: What should the reading be on a spark plug?

A3: The reading on a spark plug should be between 0.5 and 10 ohms.

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