How to Test Spark Plug with Multimeter

Test Spark Plug with Multimeter

A spark plug is an essential component of your vehicle. It helps ignite the fuel mixture inside your engine. This article will show you how to test a spark plug with a multimeter if yours needs replacing.

Spark plugs are the only major maintenance item most car owners need to check. Because they are designed to last a few thousand miles, they’re also the only significant mechanical component that most car owners don’t check. But you should check your vehicle’s spark plugs.

A multimeter is an essential instrument for testing outlets. It can tell whether your outlet is receiving power, whether white and black wires are switched, and whether it’s grounded. In the end, this tool will aid you with your questions and get started resolving most problems with outlets.

Why do we need a spark plug?a spark plug

The spark plug can describe as an electrical spark-igniting device installed inside the top of a piston inside the combustion engine. It supplies warmth to the engine’s cooling system by removing thermal energy not needed from the chamber for combustion.

Spark plugs’ primary functions are to ignite the air-fuel combination and monitor the electrification process within the engine’s pistons.


Why test spark plugstest spark plugs

Spark plug tests are methods of determining the condition of the spark plug. By checking the spark plugs in terms of resistance, voltage, and current, you will find out if they are operating properly and efficiently burning fuel.

There are many reasons to consider checking the spark plugs in your vehicle:

  • To troubleshoot potential engine problems.
  • To diagnose a misfire.
  • To carry out maintenance in advance.

How Does a Spark Plug Work?Spark Plug Works

  • Almost every tiny engine has spark plugs at the top of the camshafts. Most tiny gasoline engines are made up of these, which have cooling fins and cylinders on the outside.
  • The wire’s thickness and the fitting pushed across the end part on the end of the plug could generate electricity.
  • The engine’s ignition system can discharge an extremely high-voltage current across this wire. It is then able to move on to the spark plug. For a little engine, this typically has 20,000–30,000 Volts.
  • The end of the plug is within the chamber for combustion within the cylinder head. It stands in for the void.
  • It jumps into the airspace when high-voltage electricity meets the gap. The circuit is then completed by moving into an engine block. This causes the appearance of a spark, igniting the engine’s fuel or air mixture and allowing it to run.
  • The issues with spark plugs can be boiled down to several imperfections that prevent electrical current from bouncing to crucial electrical spark plug gaps.

Items Needed to Test the Spark Plugs

A small number of tools are needed to conduct spark plug tests. There are various professional methods of performing this, but we’ll discuss a few of the essential tools required to get started.


  • Multimeter to test resistance
  • Spark plug socket
  • Wire puller to the spark plug for older cars that do not have coil packs.


  • A spark plug
  • Sockets for cars equipped with coil packs

Safety tips when testing spark plugs

  • Take care not to get your hands on the spark plug’s connectors with your fingers.
  • Wear protective glasses when conducting tests or handling spark plugs.
  • Before starting the test, ensure the engine is shut down and cooled.
  • Before connecting the probes to the spark plug’s terminals, unplug the multimeter.
  • Avoid using spark plugs that are damaged, fouled, or malfunctioning spark plugs.
  • Make sure you use plugs specifically made for your particular engine.
  • Do not drop a spark plug into the ground because this could damage the plug.

What to look for when testing each element

Spark plugs can be evaluated by their voltage, resistance, and current, all of which provide helpful information about their health. These readings must be within the range recommended by the manufacturer of the spark plugs you use.

If the voltage, resistance, or current are too high, it may indicate that the ignition source has been damaged or is fouled. If the resistance is too small, it could be because the plug isn’t working correctly. To get reliable readings, a high-quality digital multimeter should be utilized.

Also, ensure that the plug’s terminals are dirt-free before testing. It is also recommended to test each spark plug on your engine to determine the most accurate results for the specific plug.

How to use a multimeter safely?

There are a variety of kinds as well as brands, each with different offering characteristics. In this article, we will go over the best way to utilize a multimeter in various applications in a safe manner.

However, the illustrations used in this article are generic and are not specific to any specific brand. They are to illustrate the fundamental concepts of use.

How to Test Spark Plug with Multimeter?

  1. Establishing Test

An establishing test is performed at first to test a spark plug. You can follow the underneath referenced advances:

  1. Cut off the fuel supply to the motor
  2. Remove the spark plug wire and curl the pack
  3. Remove the spark plug from the chamber head
  4. Remove the Fuel Supply to the Engine

You should draw the wire for the fuel siphon for fuel-infusion vehicles. Separate the association with the fuel siphon on the carbureted motors. Run the engine till it consumes all the fuel in the framework.

  1. Eliminate the Spark Plug Wire or Coil Pack

Fix the mounting bolt and pull the loop from the plug, particularly for vehicles with curl packs. If you have a more established motor, reassess the wire liberated from the spark plug. You can use spark plug pincers to make this cycle simple for you.

  1. Eliminate the Spark Plug from the Cylinder Head

You should eliminate the spark plug from the chamber top of the motor to check it utilizing a multimeter.

Let’s read below step by step guide to test the spark plug with the multimeter:

Test Spark Plug with MultimeterTest Spark Plug with Multimeter

Follow the steps above, then employ a multimeter for testing the plug. The steps are listed below:

  1. Select ohms on the multimeter.
  2. Check the resistance between the probes.
  3. Check the plugs
  4. View the outcomes
  1. Select Ohms on the multimeter

Ohms is the name of a unit that measures resistance and other calculations. Setting the multimeter with ohms is recommended to examine the spark plug for the most effective results.

  1. Check the resistance between the probes

Examine resistance between probes, and ensure there isn’t any resistance between the probes. This is crucial to obtain a precise reading.

  1. Check the Plugs

It is possible to check the plugs out by applying the lead connected to the terminal of the plug and another to the central electrode.

  1. Check the Reading

Examine the reading to confirm the resistances are as per the specifications. According to the manufacturer’s specifications, readings between 4,000 and 8,000 ohms are typical.

How to replace damaged plugsreplace damaged plugs

If your car’s spark plugs wear out, you should get new ones. You can buy spark plugs that are replaced from many automotive parts stores or even online. To replace the spark plugs, please follow these steps:

  • Take the spark plug that was in the past off the ignition. You may require the socket for your spark plug and a ratchet to take the plug out.
  • Examine the spark plug and make sure that it’s not damaged.
  • The new plug should be installed into the engine. You might require an ignition socket or ratchet to install this new plug.
  • Repeat steps 1-3 for each spark plug in your engine.

Many manufacturers suggest replacing your spark plugs every 30 miles. However, specific engines might require spark plugs to change more often. Refer to the owner’s manual of your vehicle for particular suggestions.

Frequently Asked Questions

How many ohms should a spark plug read?

Spark plugs are supposed to have a maximum resistance of 12,000 Ohms for each foot. However, certain OEMs of Original Equipment Manufacturers have their own unique Spark plugs’ resistance levels.

What does a weak spark look like?

A weak spark appears to be the colors orange or red. It cannot be easy to discern in the light. The best sparks show blue-white. This spark can see at any time, even in daylight. Therefore, determining a strong or weak spark isn’t rocket science.

How do you check for bad spark plugs?

There are various methods to look for defective spark plugs in a vehicle. In some instances, you’ll have to take the parts off in others instances. However, in a few cases, simply looking at the spark plugs inside the engine compartment will identify the real issue.

Wrapping Up

Assessing spark plugs and spark plug wires is equally pretty much as significant as testing every part of a motor, particularly in vehicles, before an extensive outing. No one jumps at the chance to end up abandoned in no place. Ensure you follow our aide, and you’ll be free.

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