Guide

Glow Plugs

Glow plugs are used in diesel engines to facilitate engine start-up, especially in low temperatures, and to stabilize idle engine speeds. Using glow plugs also reduces the emission of harmful components in exhaust gases during the start-up of a cold engine.

Three-phase glow plugs, used in modern diesel engines, can heat at any time before the engine starts, during its start-up, and while driving.

1. Role of Glow Plugs in an Engine:
2. How to Check Glow Plugs?
3. Glow Plugs: Symptoms of Wear
4. Can You Drive with a Glow Plug Failure?
5. Glow Plugs – What Are They?

Glow Plugs – What Are They?

Glow plugs are a crucial component in diesel engines, especially in direct-injection diesel engines. Their primary role is to provide the necessary pre-ignition temperature for fuel combustion in a diesel engine’s combustion chamber. Glow plugs serve several important functions in an engine:

• Aiding Startup: In diesel engines, especially in cold conditions, fuel can be difficult to ignite due to its density and combustion characteristics. Glow plugs heat the combustion chamber before startup, facilitating the ignition of the air-fuel mixture.
• Improving Combustion Efficiency: By providing the right pre-ignition temperature, the glow plug helps ensure optimal fuel combustion conditions in the combustion chamber. This, in turn, leads to higher combustion efficiency, which can enhance engine performance and reduce harmful emissions.
• Reducing Emissions: By ensuring complete and efficient combustion of the air-fuel mixture, glow plugs can also help reduce emissions of harmful substances like nitrogen oxides (NOx) and particulates.
• Ensuring Smooth Engine Operation: Glow plugs can also help ensure smooth engine operation, especially during startup in cold conditions, when fuel is more challenging to ignite.

These functions make glow plugs an essential element in diesel engines, and their proper functioning significantly impacts the engine’s performance, efficiency, and eco-friendliness.

How to Check Glow Plugs?

Checking the condition and efficiency of glow plugs is vital, especially in diesel engines where they play a key role in the ignition process. Here are some steps to check the condition and efficiency of glow plugs:

• Visual Inspection: Start with a visual inspection of the glow plugs. Unscrew the cables and remove the glow plugs from the cylinders. Check their electrodes and tips. Do they look clogged with soot or are they blackened? Are there any visible damages, corrosion, or contamination?
• Measuring Resistance: Use a multimeter to measure the resistance of the glow plugs. Remove them from the cylinders and connect the multimeter to the electrodes. The standard resistance value for glow plugs typically ranges from 0.6 to 2 ohms, but values can vary depending on the engine model and manufacturer.
• Checking Voltage During Startup: To check glow plugs without removing them, during an engine start attempt, you can check if the glow plug is correctly connected to the system and receiving voltage. This can be done using a voltage tester to verify if the glow plug is being properly powered during engine startup.
• Computer Diagnostics: Another way to check the plugs without removing them. In some modern vehicles, the diagnostic system can detect problems with glow plugs and display a relevant error code. If you have access to such a diagnostic scanner, you can check for any errors related to the glow plugs.

Remember, the efficiency and condition of glow plugs significantly impact the performance and ignition of a diesel engine. Therefore, regular inspection and replacement of glow plugs, when necessary, can help maintain optimal vehicle performance. If in doubt about the condition or efficiency of glow plugs, it’s best to simply replace them with new ones. Many recommend replacing glow plugs every 60,000 – 80,000 kilometers or as per the vehicle manufacturer’s recommendations. If you’re unsure how to check or replace glow plugs, it’s always worth consulting an experienced mechanic.

Glow Plugs: Symptoms of Wear

Problems with glow plugs in diesel engines can manifest in various ways, which may indicate the need for replacement or repair. Here are some symptoms to watch for:

• Difficulty Starting the Engine: Damaged or worn glow plugs can cause difficulty in starting the engine, especially on cold days. If the engine doesn’t start or takes longer to start, the condition of the plugs might be the problem.
• Slow Engine Warming: If glow plugs are not functioning properly, the engine may take longer than usual to warm up, especially in cooler conditions.
• Uneven Engine Performance: Damaged or faulty glow plugs can lead to uneven engine operation. There might be jerking, vibrations, or irregular engine performance while driving.
• Increased Smoke Emission: Damaged glow plugs can cause incomplete fuel combustion, leading to increased exhaust smoke, especially at startup or during acceleration.
• Decreased Fuel Efficiency: Worn or faulty glow plugs can lead to reduced fuel efficiency, meaning the car may consume more fuel than usual.
• Check Engine Light: Damaged glow plugs can also trigger the check engine light on the dashboard. In some vehicles, electronic diagnostic systems can detect glow plug operation issues and generate corresponding error codes.

If you experience any of these symptoms, it’s worth consulting an experienced mechanic who can accurately diagnose the problem and recommend appropriate corrective actions. Often, replacing worn or damaged glow plugs can restore proper engine function and improve its efficiency.

Glow Plug Failure in the Engine – Can You Still Drive?

If a glow plug failure occurs in a diesel engine, certain precautions may be necessary, but whether you can continue driving depends on several factors, such as the extent of the plug damage and driving conditions. Here are some considerations:

• Weather Conditions: In colder conditions, glow plug failure can make starting the engine difficult or even impossible. If the temperature is low, the absence of functioning glow plugs can cause difficulties in starting the engine.
• Consequences for the Engine: Continuing to drive with damaged glow plugs can lead to uneven engine operation or a decrease in performance. In extreme cases, this can cause damage to other engine components.
• Emission of Exhaust Gases: Damaged glow plugs can lead to incomplete fuel combustion, which may increase the emission of harmful substances. This can impact health and the environment.
• Error Code: If the engine control light on the dashboard indicates a problem with the glow plugs, diagnose the problem and take appropriate corrective steps as soon as possible.

In the case of glow plug failure, it’s recommended to consult with a mechanic or a diesel engine specialist as soon as possible. If you plan to continue driving, be prepared for difficulties in starting the engine or potential performance issues. In any case, safety is paramount, so if you’re unsure whether you should continue driving, it’s better to stop and seek professional advice.

How to Remove and Replace Glow Plugs: Step by Step

Here are the steps to remove (and replace) glow plugs:

1. Wait Until the Engine Cools Down: Make sure the engine is completely cold before starting work. Attempting to remove a plug from a hot engine can damage the threads or other components.
2. Locate the Glow Plug: Find and locate the glow plug in the engine. Glow plugs are usually located in the cylinder head and sometimes covered by a shield or cover.
3. Turn Off the Engine: Turn off the engine to prevent accidental startup during work.
4. Remove the Cover: If the plug is covered, remove the cover or shield to access the plug.
5. Remove the Plug: Use the appropriate socket wrench (usually a deep socket) to unscrew the glow plug from the cylinder head. Ensure the wrench fits properly to avoid damaging the plug or threads. Special deep socket wrenches are often used for this purpose, designed with notches for a secure fit on the plug head. There are different socket sizes corresponding to different glow plug sizes, so it’s important to choose a wrench of the appropriate size for the specific engine plugs. Before purchasing a socket wrench, check the specifications of the glow plugs used in your engine to select a wrench of the correct size. Additionally, there are socket wrenches with magnetic holders that facilitate the extraction and installation of plugs in hard-to-reach places.
6. Unscrew Carefully: Unscrew the plug carefully to avoid damaging the thread or other components. Be careful not to tilt the plug while removing it.
7. Check the Condition of the Plug: After removing the plug, examine its condition. Check for excessive wear, corrosion, or other damages that might affect engine performance.
8. Replace with a New One: If the plug is worn or damaged, replace it with a new one. Ensure that the new plug is appropriately matched to the engine and has the correct specifications.
9. Installing the New Plug: Carefully insert the new plug into the cylinder head and gently tighten it using a socket wrench. Ensure it is tightened to the right torque but not too tightly to avoid damaging the threads. The correct tightening torque is crucial for proper operation and sealing in the engine’s cylinder head. Car manufacturers usually provide specific torque values for different models and types of engines. It is safest to check the vehicle’s manual or parts catalog recommended by the manufacturer to find the right torque for tightening glow plugs. This is important as under-tightening can lead to leaks or improper sealing, while over-tightening can damage the threads or even break the plug.
10. Reinstall the Cover: If the plug was covered, reinstall the cover or shield in its place.

Removing glow plugs requires precision and caution. If you’re unsure how to do it, or if you have any doubts, it’s better to consult an experienced automotive mechanic.