Symptoms of bad Glow Plugs: (Testing & Replacement cost)

Symptoms of bad Glow Plugs: (Testing & Replacement cost)

Glow plugs play a crucial role in the proper functioning of diesel engines. These small components are responsible for heating the engine’s air-fuel mixture, ensuring a smoother and more efficient combustion process. However, like any other part in an engine, they can deteriorate over time and cause various problems.

In this article, we will discuss the symptoms of bad glow plugs, how to test them, and the cost of replacement. Whether you’re a vehicle owner or a mechanic, understanding the warning signs and proper testing procedures can save you from costly repairs and ensure your engine is running at its best. So, let’s dive into the world of glow plugs and learn how to identify and address any potential issues.

Table of Contents

Diesel Engine glow plugs working principles.

Diesel Engine glow plugs working principles.

A diesel engine is a type of internal combustion engine that uses the heat generated by compressing air in the combustion chamber to ignite the fuel. Unlike gasoline engines that use spark plugs, diesel engines use glow plugs to start the combustion process.

Glow plugs are heating devices installed in the combustion chamber of a diesel engine. They are similar in appearance to spark plugs but work differently. The basic principle behind the functioning of a glow plug is to preheat the air in the combustion chamber before injecting the diesel fuel. This is necessary because diesel fuel requires high temperature to vaporize and ignite.

The working principle of a glow plug involves the application of electrical current to heat a platinum or ceramic coil located within the plug. When voltage is applied, the coil heats up and starts to glow, hence the name “glow plug.” This heating element can reach temperatures of up to 1,900 degrees Fahrenheit in just a few seconds.

When the driver turns the key in the ignition, the glow plugs start heating up and continue to do so for a few seconds depending on the outside temperature. This enables the air in the combustion chamber to reach a higher temperature, making it easier to ignite the diesel fuel. Once the engine starts and the combustion process is sustained, the glow plugs turn off.

Some newer diesel engines use a system called “glow plug control module” which uses sensors to determine the outside temperature and adjust the heating time of the glow plugs accordingly. This ensures optimal heating of the air in the combustion chamber for efficient ignition of the diesel fuel.

It is important for the glow plugs to function properly for the diesel engine to start easily, especially in cold weather conditions. A faulty glow plug can result in difficulty starting the engine or even complete failure to start.

What are the symptoms of bad glow plugs?

What are the symptoms of bad glow plugs?

Glow plugs are vital components of diesel engines and play a crucial role in the combustion process. These small but powerful devices have a direct impact on the performance and efficiency of a diesel engine. When they are in good condition, they heat up the engine’s combustion chamber and help ignite the fuel, allowing the engine to start smoothly.

However, if the glow plugs start to fail or become faulty, it can lead to a range of issues and symptoms that can affect the overall functioning of the engine. In this article, we will discuss the symptoms of bad glow plugs.

1. Difficulty starting the engine

One of the primary symptoms of bad glow plugs is difficulty starting the engine, especially in colder temperatures. As mentioned earlier, glow plugs are responsible for heating up the combustion chamber, which is necessary for diesel engines to ignite the fuel.

If the glow plugs are not functioning correctly, the engine will have a hard time starting, and you may have to keep cranking the engine for an extended period before it finally starts. This can also lead to excessive smoke coming out of the exhaust pipe when the engine does start.

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2. Misfiring and rough idling

Misfiring is a common symptom of bad glow plugs. This happens when the glow plugs fail to heat up the combustion chamber efficiently, causing the fuel to not burn evenly. As a result, the engine may have a rough idle and may vibrate or shake. You may also notice a loss of power and a decrease in fuel efficiency. If left unaddressed, this can lead to more severe issues like damaged piston rings, valves, and cylinders.

3. Check engine light

Most modern diesel engines have an onboard computer system that monitors the engine’s performance. This system can detect a faulty glow plug and will trigger the check engine light. The check engine light can indicate various issues, but if you notice it along with other symptoms, it is likely due to bad glow plugs.

4. Engine hesitation and surging

Another symptom of bad glow plugs is engine hesitation and surging. This occurs when the combustion chamber does not get enough heat to ignite the fuel efficiently. As a result, the engine may hesitate or surge while accelerating, making it challenging to maintain a steady speed.

5. Hard or black starting smoke

A diesel engine that is in good condition should not produce excessive smoke, especially at start-up. However, if you notice dark or black smoke coming out of the exhaust pipe when starting the engine, it may be due to bad glow plugs. This happens because the fuel is not burning efficiently, and the unburnt fuel particles are being expelled as smoke.

How to test glow plugs

How to test glow plugs

Glow plugs are an essential component in diesel engines, used to heat up the air inside the combustion chamber during cold weather conditions. Testing the functionality of glow plugs is crucial in ensuring the smooth operation and efficiency of diesel engines. In this article, we will discuss the steps involved in testing glow plugs.

1. Visual Inspection

The first step in testing glow plugs is to visually inspect them for any signs of physical damage or wear and tear. Look for any signs of corrosion, bending, or broken terminals. If you notice any damage, immediately replace the glow plugs.

2. Using a Multimeter

A multimeter is a versatile tool that can be used to test various electrical components, including glow plugs. Set your multimeter to the resistance (ohms) function and connect the positive and negative leads to the respective terminals of the glow plug. The reading on the multimeter should be between 0.4 to 2 ohms. If the reading is significantly higher or lower, it indicates a faulty glow plug.

3. Conduct a Power Test

With the engine turned off, disconnect the wires connected to the glow plug relay and connect a test light to the positive terminal of the battery. Touch the exposed end of the glow plug wire to the negative terminal of the battery. If the light turns on, it indicates that the glow plug is receiving power. Repeat the process for all the glow plugs.

4. Check the Time it Takes to Heat Up

One of the critical functions of glow plugs is to heat up the air inside the combustion chamber. If the glow plugs take a longer time to heat up, it indicates a faulty plug. Use a timer to check the time it takes for the glow plug to heat up. The ideal time should be between 3 to 7 seconds.

5. Examine the Appearance of the Glow Plug

A properly functioning glow plug will have a smooth, brown tip after use, indicating that it has reached the desired temperature. If the tip appears burnt, black, or covered in carbon deposits, it indicates a faulty glow plug.

6. Conduct a Resistance Test After Running the Engine

For a more accurate test, you can run the engine for a short while and then perform the resistance test again. If the resistance has increased significantly, it indicates a faulty glow plug.

7. Test the Glow Plug Relay

The glow plug relay is responsible for sending power to the glow plugs. Faulty relays can result in one or more glow plugs not receiving power. To test the relay, use a jumper wire to connect the battery’s positive terminal to the relay’s switch terminal. If the glow plugs receive power, it indicates a faulty relay.

How to buy glow plugs

How to buy glow plugs

Glow plugs are essential components in diesel engines as they help in starting up the engine by heating up the compressed air in the combustion chamber. When shopping for glow plugs, it is important to ensure that you are getting the right ones for your engine. Here are some tips on how to buy glow plugs:

1. Know your engine’s specifications

The first step in buying glow plugs is to know the specifications of your engine. This includes the make, model, and year of your vehicle. Glow plugs come in different sizes and shapes, so it is crucial to get the ones that are specifically designed for your engine.

2. Check the resistance

The resistance of a glow plug is a significant factor in its performance. It is measured in ohms, and you can find this information in the manufacturer’s manual. Make sure that the resistance of the glow plugs you are buying matches that of your engine to ensure proper functioning.

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3. Consider the heat rating

The heat rating of a glow plug determines how quickly it can heat up the air in the combustion chamber. This is important for a smooth and fast startup of the engine. If the heat rating is too low, the engine may struggle to start, and if it is too high, it may cause overheating. Refer to your engine’s manual to determine the recommended heat rating for your glow plugs.

4. Look for high-quality materials

Glow plugs are usually made of either metal or ceramic. It is essential to opt for high-quality materials as they ensure durability and longevity of the glow plugs. Low-quality materials may result in frequent replacements and potential damage to the engine.

5. Consider the thread size

Glow plugs have different thread sizes, so it is vital to ensure that the ones you are buying have the same thread size as the ones you are replacing. Mismatched thread sizes can cause air leakage, resulting in engine performance issues.

6. Buy from reputable brands and sellers

It is important to purchase glow plugs from reputable brands and sellers to ensure that you are getting genuine and high-quality products. Do some research and read reviews to determine the best brands in the market.

7. Check for warranty

Glow plugs can be a significant investment, so it is crucial to make sure that they come with a warranty. This will protect you from any defects or malfunctions and give you peace of mind.

How to replace glow plugs

How to replace glow plugs

Replacing glow plugs is an essential maintenance task for diesel engine vehicles. Glow plugs play a crucial role in the ignition process of diesel engine vehicles, as they heat the compressed air inside the engine’s cylinders to facilitate the combustion of the fuel.

Over time, glow plugs can wear out or become damaged, leading to starting issues and poor engine performance. In this article, we will discuss the steps to replace glow plugs in a diesel engine vehicle.

Step 1: Gather the necessary tools and materials

To replace glow plugs, you will need the following tools and materials:

  • New glow plugs
  • Socket wrench
  • Glow plug socket (specifically designed for diesel engines)
  • Torque wrench
  • Anti-seize lubricant
  • Clean rag
  • Wire brush
  • Multi-meter (optional)

Step 2: Park the vehicle in a safe and flat area

Make sure to park your vehicle on a flat surface and turn off the engine. Put the vehicle in park and engage the parking brake to avoid any movement during the process.

Step 3: Locate the glow plugs

The glow plugs are typically located on the cylinder head, near the intake manifold. Refer to your vehicle’s manual to find the exact location of the glow plugs.

Step 4: Remove the cover over the glow plugs

Using a socket wrench, remove the cover over the glow plugs. Some vehicles may have individual covers for each glow plug, while others may have a single cover for all the glow plugs.

Step 5: Remove the glow plugs

Using a glow plug socket, remove the old glow plugs one at a time. Be careful not to damage the threads of the glow plugs or the surrounding area.

Step 6: Inspect the old glow plugs

Check the condition of the old glow plugs. If they are damaged or worn out, they will need to be replaced.

Step 7: Clean the threads of the glow plug aperture

Using a wire brush, clean the threads of the glow plug aperture to remove any debris or build-up. This will ensure that the new glow plugs can be screwed in easily and securely.

Step 8: Apply the anti-seize lubricant

Apply a small amount of anti-seize lubricant to the threads of the new glow plugs. This will help prevent them from seizing in the future and make it easier to remove them during the next replacement.

Step 9: Install the new glow plugs

Using the glow plug socket and torque wrench, tighten the new glow plugs to the manufacturer’s recommended torque specification. Be careful not to over-tighten them, as this can damage the threads.

Step 10: Reattach the cover over the glow plugs

Put the cover back over the glow plugs and tighten it with the socket wrench.

Step 11: Test the new glow plugs

If you have a multi-meter, you can test the resistance of the glow plugs to ensure they are working correctly. If not, start the engine and let it run for a few minutes to allow the new glow plugs to heat up and ensure they are functioning properly.

Step 12: Repeat for all glow plugs

Repeat the above steps for all the glow plugs in your vehicle. It is recommended to replace all glow plugs at the same time, even if only one is damaged or worn out.

How much does it cost to replace new glow plugs?

How much does it cost to replace new glow plugs?

Glow plugs are an essential component of diesel engines, as they provide the necessary heat to ignite the fuel in the combustion chamber. Over time, these plugs can wear out or become damaged, requiring replacement.

The cost of replacing glow plugs can vary depending on the make and model of the vehicle, the number of plugs that need to be replaced, and where you live. In this article, we will discuss the average cost of replacing new glow plugs and factors that can affect the overall cost.

On average, the cost of replacing new glow plugs can range from $80 to $250 per plug. This cost includes the price of the glow plugs themselves, labor charges, and any additional parts or services that may be needed during the replacement process. Most vehicles have between 1 and 8 glow plugs, meaning that the total replacement cost can range from $80 to $2,000.

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One of the main factors that can affect the cost of replacing glow plugs is the make and model of your vehicle. Some vehicles have easier access to the glow plugs, making the labor cost lower. For example, replacing glow plugs on a Ford F-150 can cost around $150 per plug, while the same service on a Mercedes-Benz GL-Class can cost up to $250 per plug.

Another factor that can affect the cost is the type of glow plugs being replaced. There are two main types of glow plugs – standard and quick-start. Quick-start glow plugs are designed to heat up faster and last longer, making them more expensive than standard glow plugs. If your vehicle requires quick-start glow plugs, the cost of replacement can be higher.

The location of your vehicle can also play a role in the cost of replacing glow plugs. If you live in a major city with a high cost of living, you can expect to pay more for labor charges compared to living in a smaller town. Other charges such as taxes and fees can also vary depending on your location.

In addition to the cost of the glow plugs and labor charges, there may be additional parts or services needed during the replacement process. For example, if the glow plugs are difficult to access, the mechanics may need to remove other engine components, which can increase the labor cost. Additionally, if the glow plugs caused damage to other parts of the engine, there may be added costs for repairs or replacements.

It is important to note that the cost of replacing new glow plugs can also vary based on where you get the service done. For example, getting your vehicle serviced at a dealership can be more expensive than taking it to a local mechanic. However, taking your vehicle to a certified dealership can ensure that you are getting high-quality, genuine glow plugs and expert service.

Conclusion

In conclusion, knowing the symptoms of bad glow plugs and how to test and replace them is crucial for maintaining a healthy engine. From sluggish starts and decreased fuel efficiency to engine misfires and smoke emissions, these signs indicate the need for a replacement. While the cost of replacing glow plugs may vary depending on the make and model of your vehicle, it is important to address this issue promptly to prevent further damage and costly repairs.

With proper maintenance and regular testing, you can ensure the longevity and performance of your glow plugs. Remember, when in doubt, consult a trusted mechanic for professional help. Taking care of your glow plugs will ultimately improve your driving experience and save you time and money in the long run.


Frequently Asked Questions

What is the role of glow plugs in a diesel engine?

Glow plugs play a crucial role in diesel engines by heating the air-fuel mixture in the combustion chamber, facilitating efficient ignition, especially in cold conditions.

How do glow plugs work in a diesel engine?

Glow plugs preheat the air in the combustion chamber using an electrical current, reaching temperatures up to 1,900 degrees Fahrenheit. This makes it easier to ignite the diesel fuel during the starting process.

What are the symptoms of bad glow plugs?

  • Difficulty starting the engine: Especially in colder temperatures.
  • Misfiring and rough idling: Uneven burning of fuel leading to engine vibration.
  • Check engine light: Triggered by a faulty glow plug.
  • Engine hesitation and surging: Difficulty maintaining a steady speed while accelerating.
  • Hard or black starting smoke: Excessive smoke during startup, indicating inefficient fuel combustion.

How can I test glow plugs?

  • Visual Inspection: Check for physical damage or wear.
  • Multimeter Test: Measure resistance (ohms) of glow plugs.
  • Power Test: Check if glow plugs receive power when the engine is off.
  • Heating Time Test: Measure the time it takes for the glow plug to heat up.
  • Post-Run Resistance Test: Test resistance after running the engine for accuracy.
  • Glow Plug Relay Test: Check the relay responsible for sending power to glow plugs.

What should I consider when buying glow plugs?

  • Engine Specifications: Know your engine’s make, model, and year.
  • Resistance: Match the resistance of the glow plugs to your engine’s specifications.
  • Heat Rating: Choose a heat rating suitable for efficient startup.
  • Material Quality: Opt for high-quality metal or ceramic glow plugs for durability.
  • Thread Size: Ensure the new glow plugs have the same thread size as the old ones.
  • Reputation: Purchase from reputable brands and sellers.
  • Warranty: Check for warranty to protect against defects.

How can I replace glow plugs?

  • Gather Tools: Collect necessary tools and materials, including new glow plugs.
  • Park Safely: Park on a flat surface, turn off the engine, and engage the parking brake.
  • Locate Glow Plugs: Refer to the manual to find the location of the glow plugs.
  • Remove Cover: Use a socket wrench to remove the cover over the glow plugs.
  • Remove Old Glow Plugs: Using a glow plug socket, remove old glow plugs one at a time.
  • Inspect and Clean: Check the condition of old glow plugs and clean the threads.
  • Apply Lubricant: Apply anti-seize lubricant to the threads of new glow plugs.
  • Install New Glow Plugs: Tighten new glow plugs to the recommended torque specification.
  • Reattach Cover: Put the cover back and tighten it.
  • Test New Glow Plugs: Test for resistance or start the engine to ensure proper function.
  • Repeat for All Plugs: Repeat the process for all glow plugs.

How much does it cost to replace glow plugs?

The cost of replacing glow plugs varies based on factors like the vehicle’s make and model, the number of plugs, and labor charges. On average, it can range from $80 to $250 per plug, with total costs potentially reaching $2,000. Factors such as quick-start glow plugs, location, and additional repairs can influence the overall cost.


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