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How to Test an Ignition Coil with Multimeter (+ faulty symptoms)

If your car misfires whenever you try to accelerate or it simply fails to start, your ignition coil may be the source of the problem. You will find a comprehensive guide on how to test your ignition coil in this article.
Stephanie Lawrence
Stephanie Lawrence
12/27/2022 · 8 min read
ignition coil ignition coil ignition coil

Car problems can cause significant disruptions in our daily lives.

If you're having issues with your ignition system, such as your car misfiring whenever you try to accelerate or the engine simply failing to start, your ignition coil could be the source of the problem.

We're here to provide you with a comprehensive guide on how to test your ignition coil as well as some indicators that it's time to replace it.

Table of Contents

  • What is an Ignition Coil
  • What causes damage to an ignition coil
  • How to spot a faulty Ignition coil
  • How to test an ignition coil with a digital multimeter
  • What happens if I don’t replace the ignition coil?
  • FAQs About Ignition Coils

What is an Ignition Coil

An ignition coil is a type of electrical transformer that is used to boost the voltage of an internal combustion engine's ignition system. It generates a spark at the spark plug, which ignites the fuel, resulting in the combustion required to power the engine. The ignition coil is critical to the proper operation of an engine because it is responsible for igniting the fuel and air mixture at the precise moment required for the engine to run.

What does it do

As previously stated, the ignition coil is in charge of converting the low voltage of the battery into the high voltage required to produce an electric spark in the spark plugs. This high voltage is responsible for igniting the fuel-air mixture in the engine's cylinders, causing the engine to run. The engine would not be able to start or run without the ignition coil.

Why is it essential?

The ignition coil is necessary because it generates the spark required to ignite the fuel and produce combustion, without which the engine cannot function. It is also required because the increased voltage supplied by the ignition coil is required to generate the spark. Without it, the spark would be insufficiently powerful to ignite the fuel, resulting in the engine failing to start.

What causes damage to an ignition coil

An ignition coil can be damaged by a number of factors. Some of the most common causes of damage are:

Overheating: If the ignition coil is used for extended periods of time at high engine speeds or if it is placed in a hot environment, it can become overheated. Overheating can cause the coil's insulation to deteriorate, resulting in electrical shorts and other issues.

Vibration: The ignition coil is subjected to a lot of vibration when the engine is running. Over time, this can cause the coil's internal components to become loose or damaged, which can affect its performance.

Physical damage: If the ignition coil is physically impacted by something, such as a rock or piece of debris, it can be damaged. This can result in the coil's internal components becoming damaged or broken, affecting its performance.

Moisture: Because the ignition coil contains electrical components that can be damaged by water, it is vulnerable to moisture damage. Moisture can cause the coil's insulation to deteriorate, resulting in electrical shorts and other issues.

Age: The ignition coil can simply wear out and become less effective over time. This is typically due to the cumulative effects of heat, vibration, and other factors, which can cause the coil's internal components to fail.

In general, it is important to keep the ignition coil in good condition to ensure that it continues to function properly. This may involve regular maintenance and inspections, as well as replacing the coil if it becomes damaged or fails.

Signs of damages

There are a few indications that an ignition coil is damaged or failing. Some common symptoms include:

  • The engine starts slowly or does not start at all.
  • The engine misfires or runs erratically.
  • The check engine light is illuminated.
  • The vehicle's power or acceleration is reduced.
  • While driving, the vehicle stalls or hesitates.
  • The fuel efficiency has decreased noticeably.

If you notice any of these symptoms, have the ignition coil checked by a mechanic to see if it is the source of the problem. They will be able to diagnose the problem and recommend a solution, such as replacing the ignition coil if necessary.

How to spot a faulty Ignition coil

A faulty ignition coil can be identified in several ways. The following are some common indications that an ignition coil is faulty:

  • The engine starts slowly or does not start at all.
  • The engine misfires or runs erratically.
  • The check engine light is turned on.
  • The vehicle's power or acceleration is reduced.
  • While driving, the vehicle stalls or hesitates.
  • The fuel efficiency has decreased noticeably.

If you find any of these symptoms, have the ignition coil checked by a mechanic to see if it is the source of the problem. They will be able to diagnose the problem and recommend a solution, such as replacing the ignition coil if necessary.

Is it safe to drive with a damaged ignition coil?

Driving with a damaged ignition coil is generally unsafe. A faulty ignition coil can cause a variety of issues with your vehicle, including engine misfires, power loss, and decreased fuel efficiency. It can even cause the engine to stall or fail completely while driving in some cases, which can be dangerous.

If you suspect that your ignition coil is damaged, take it to a mechanic as soon as possible. They will be able to diagnose the issue and recommend a solution, such as replacing the ignition coil if necessary. Meanwhile, avoid driving the vehicle if possible to avoid further damage or potential safety issues.

What to do if your ignition coil is faulty

The first thing you should do if you suspect your ignition coil is faulty is to contact a mechanic for a diagnostic check. They will be able to determine whether the ignition coil is the source of the problem and recommend the best course of action. Most of the time, this will entail replacing the ignition coil.

If the ignition coil is found to be faulty, it should be replaced as soon as possible. A faulty ignition coil can cause a variety of issues with your vehicle, including engine misfires, power loss, and decreased fuel efficiency. It can even cause the engine to stall or fail completely while driving in some cases, which can be dangerous.

While it is possible to replace the ignition coil yourself if you have prior automotive repair experience, it is generally recommended that it be done by a professional. Ignition coils are delicate components, and improper installation can result in additional vehicle damage. A mechanic will have the tools, knowledge, and experience required to replace the ignition coil correctly, ensuring that your vehicle runs safely and efficiently.

How to test an ignition coil with a digital multimeter

To test an ignition coil with a digital multimeter, follow these steps:

Follow these steps to test an ignition coil with a digital multimeter:

  • Set the multimeter to the resistance setting (usually denoted by a delta symbol (Ω).
    Disconnect the ignition coil from the electrical system of the vehicle.
  • Touch one probe of the multimeter to the primary terminal of the ignition coil and the other probe to the secondary terminal.
  • Check the multimeter reading. It should be within the resistance range specified by the manufacturer. If the reading falls outside of this range, the ignition coil is likely to be defective and should be replaced.
  • Repeat the test by connecting the ignition coil to the vehicle's electrical system. This will put the coil's secondary winding to the test, which is responsible for generating the high voltage required to spark the spark plugs.
  • Connect one probe to the battery's positive terminal and the other to the ignition coil's primary terminal to test the coil's primary winding.
  • Turn on the ignition and look at the multimeter reading. It should show a voltage drop, indicating that the primary winding of the coil is working properly. If no voltage drop occurs, the ignition coil is likely faulty and should be replaced.

It is important to follow these steps carefully to ensure that the ignition coil is tested properly. If you are unsure about how to test an ignition coil with a digital multimeter, it is best to consult a mechanic or refer to the vehicle's repair manual for assistance.

Tools required

To test an ignition coil with a digital multimeter, you will need the following tools:

  • Digital multimeter: This is an electronic device that is used to measure various electrical properties, such as voltage, current, and resistance. Most multimeters have multiple settings and ranges that allow you to test different components in a vehicle's electrical system.
  • Ignition coil: This is the component that you will be testing. The ignition coil is typically located near the engine and is responsible for converting the low voltage from the battery into the high voltage needed to create a spark in the spark plugs.
  • Wrench: Depending on the vehicle, you may need a wrench to remove the ignition coil from the engine. This will typically be a socket wrench or a box wrench, depending on the size and type of fasteners used to secure the ignition coil.
  • Test leads: These are the probes that are used with a multimeter to test the ignition coil. Most multimeters come with a set of test leads, but you can also purchase them separately if needed.
  • Safety equipment: It is always important to wear appropriate safety equipment when working on a vehicle. This may include gloves, safety glasses, and other protective gear to prevent injury.
  • Vehicle repair manual: This is a reference guide that provides detailed instructions for testing and repairing various components in a vehicle. A repair manual can be helpful if you are unsure about how to test the ignition coil or if you need additional information about the vehicle's electrical system.

Having these tools on hand will help you test the ignition coil properly and safely. It is important to follow the instructions carefully and to use the correct tools to avoid damaging the ignition coil or the vehicle's electrical system.

What happens if I don’t replace the ignition coil?

A faulty ignition coil can cause a variety of issues with your vehicle if it is not replaced. Some of the most common issues are:

The engine may be difficult or impossible to start. This can be inconvenient and frustrating because it may prevent you from driving the vehicle.

The engine may misfire or run erratically. This can have an impact on the vehicle's performance and make it difficult to drive smoothly.

The vehicle's power or acceleration may be reduced. This can make driving at higher speeds or merging onto a highway difficult.

While driving, the vehicle may stall or hesitate. This can be dangerous because it can cause the vehicle to lose control or come to a sudden stop.

There could be a noticeable drop in fuel efficiency. Because you will need to fill the tank more frequently, the cost of operating the vehicle will rise.

To avoid these issues, it is critical to replace a faulty ignition coil as soon as possible. A mechanic can diagnose the issue and recommend the best course of action, such as replacing the ignition coil if necessary. This will aid in the safe and efficient operation of your vehicle.

FAQs About Ignition Coils Testing

What is the life expectancy of an ignition coil?

The life expectancy of an ignition coil is determined by a number of factors, including frequency of use, ignition coil quality, and engine maintenance. In general, an ignition coil can last between 30,000 and 100,000 miles. Regular maintenance and inspection of the ignition coil, on the other hand, is recommended to ensure that it is working properly and does not need to be replaced.

Can ignition coils be cleaned?

Yes, ignition coils can be cleaned, but only with care and using the proper tools. Before cleaning the ignition coil, make sure the engine is turned off and the ignition switch is in the "off" position. Furthermore, special cleaners should be used to avoid damaging the coil during the cleaning process.

How often should an ignition coil be replaced?

There is no set schedule for replacing an ignition coil because the coil's lifespan varies depending on a number of factors. However, most ignition coils are designed to last at least 100,000 miles, if not more.

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