Glow Plug Warning Light Issue [Causes And How To Fix]

ALEX HARPER

The glow plug plays an important role in diesel engines’ engine management systems. Gasoline engines use them to replace spark plugs. In cold weather conditions, when starting the engine is difficult, glow plugs ensure that your vehicle starts with ease. Preheaters and heaters are used in engines to enable easy combustion by preheating and heating the cylinders.

The engine relies on them to last for a long time. Regular use, however, can cause them to fail over time. Symptoms of bad glow plugs are discussed in this article. I’ll start by explaining how they work.

Glow Plug Warning Light Issue

Glow plug principles for diesel engines

Essentially a piece of metal with a heating element on top, a glow plug is an essential part of a diesel engine. The shape is similar to that of a pencil.

Air and fuel mix in petrol engines are ignited by spark plugs. Diesel engines, however, start with glow plugs. To make sure the combustion chamber reaches the required temperature, the glow plugs heat the air.

The glow plugs become electrified when the ignition is turned on. Heat is generated as a result, resulting in orange to red color emission from the heating element. Combustion begins when the heated glow plug ignites the air-fuel mixture in the combustion chamber.

There’s one glow plug per cylinder, just like in petrol engines. The number of cylinders determines how many glow plugs there are in a diesel engine.

How can you tell if a glow plug is bad?

There are a number of reasons for the engine warning light to illuminate. The engine starts harder, it misfires, it idles rough, its fuel efficiency decreases, a glow plug failure occurs, the engine starts harder, it misfires, the engine starts more slowly, the engine’s exhaust pipe will produce white smoke and black smoke, and the engine is going to emit white smoke as well as black smoke.

An engine check light will appear

There is usually something wrong with the engine when the check engine light comes on. Check engine light will illuminate when glow plugs fail, triggering a warning from the car computer. The check engine light, however, may be triggered by a variety of factors. If the warning light appears on your dashboard, you must diagnose the problem.

It will be difficult to start the engine

Glow plug problems are most commonly associated with hard starting. It is impossible to burn diesel and start the engine if the glow plug is faulty. Having bad glow plugs prevents diesel engines from starting.

A misfire has occurred in the engine

Compression, diesel injection, and high temperatures all play a role in diesel engines burning efficiently. No matter how much equipment you have, combustion won’t occur if the combustion chamber isn’t heated up enough.

Is it possible to lose power when glow plugs are faulty? Your guess is correct! Compression, fuel quality, and fuel injection problems will lead to misfiring of the diesel engine.

Burning requires heat, which is provided by compression pressure and glow plugs. 232 degrees Celsius or 450 degrees Fahrenheit is the temperature that a combustion chamber needs to achieve in order to ignite. Due to the internal pressure of the combustion chamber, the engine cannot run at its best efficiency with damaged glow plugs.

Idling is rough on the engine

It will be difficult to start the engine if there is any damage to the glow plug or if carbon has built up on it. In addition, the engine won’t stay running once it is started. Rough idling refers to this. In addition to this, a bad glow plug relay may also cause this problem. White smoke will result from rough idling.

White smoke is emitted from the exhaust

It is commonly associated with insufficient heat for fuel to burn properly when white smoke is produced. Unburned fuel particles will be exhausted by the engine. The tailpipe will smell of fuel in such cases. In cold climates, diesel exhaust usually produces white smoke.

Lousy glow plugs and damaged glow plug control modules are the most common causes of white smoke from the exhaust. A low cranking speed, low compression, and air in the fuel system can also cause white smoke to appear.

A worn injector pump, delayed injection timing, or faulty injectors may cause the white smoke even after the engine gets hot.

Exhaust smoke is black in color

Air-fuel ratios that are too rich cause black smoke. Fuel is pumped into the engine at too high a rate, and air is not provided. The burning chamber isn’t going to burn 100% of fuel when you use lousy glow plugs. By doing this, the O2 sensor will sense that the engine is receiving too much fuel.

Black smoke usually emanates from the tailpipe when unburned fuel is present. Glow plugs or other vital engine components may be malfunctioning, which is why black smoke is produced.

Fuel efficiency is low

Diesel engines cannot be optimized based on plugs since fuel and temperature determine fuel efficiency. Glow plugs, however, have an effect on engine temperature.

Having lousy glow plugs is detrimental to diesel engines, since the fuel must be heated before combustion can happen. In response, the engine will have to work harder. Gas mileage will suffer as a result.

Let me just pause for a moment. Where do glow plugs come from? Only engines are started with them? The glow plug serves primarily to start the engine. Glow plugs are now used to measure combustion chamber temperature.

Car manufacturers are advancing glow plug technology. Glowing plugs are now equipped with Glow Combustion Sensors (GCSs). With this technology, the car’s computer measures the temperature in the combustion chamber. In order to determine how much air and fuel should be added, the PCM uses this information.

How To Test Glowing Plugs?

How To Test Glowing Plugs?

Glow plugs can be tested in several ways. The battery-based glow plug testing and the glow plug resistance test will be our main focus. Resistance testing is more accurate than the other two.

However, make sure that your multimeter is set up so that low resistance readings are accurate before you embark on the resistance test. The resistance of glow plugs typically ranges from 1 to 6Ω. It is best to get a new multimeter if yours is unable to obtain such small readings.

We’ll begin by testing resistance

  • There should be no power connected to glow plugs. Taking individual measurements of glow plugs would be tedious if you did not do it.
  • Make sure your multimeter’s resistance is as low as possible
  • On the engine ground, place the multimeter probe near the glow plug
  • Power the glow plug with a red probe
  • Turn on the glow plugs
  • Record your readings using the multimeter. Glowing plugs shouldn’t be more than 6Ω.
  • Don’t forget to turn the glow plugs off
  • Disconnect the red probe from the glow plug tip
  • Follow these steps to make sure you’re reading all glow plugs accurately.

Glow plugs can be tested without removing them in the step above. Before you do this, you can remove the glow plugs. Glow plugs should be removed by inserting the black multimeter probe into the hex thread. After that, it is necessary to connect the red probe to the plug tip.

Battery-powered glow plug testing

A standalone test is not being conducted here. Here, the results from the previous tests are confirmed to ensure they are accurate. The battery test should be performed without the glow plugs.

  • Engine glow plugs must be removed.
  • The glow plug tip needs to be connected to one wire and the hex needs to be connected to the other wire.
  • The negative battery terminal should be connected to the hex wire
  • A positive battery terminal should be connected to the tip wire
  • It is important to test a glow plug within 10 seconds of turning it hot red.

Glow plug buying guide

You will have a much easier time finding the right replacement glow plug if you are still using the original OEM glow plug. Whenever you order online or at a local shop, you must take the OE part number with you.

Lockup search is available on some online stores’ websites. The glow plug that will fit your car can be found by entering the number plate. Following the recommended number plate will result in optimal performance.

In the event that the OE plug has been replaced, you should obtain another glow plug with the same serial number. Making an informed purchasing decision is made easier when you have this information at your disposal.

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Glow plug replacement

Unless the test light is bad, it is best to replace faulty glow plugs after testing them with a test light or any other method. The following instruction will show you how to replace glow plugs in an easy and straightforward manner

  • Battery terminals should be disconnected
  • Valve cover may need to be removed if needed
  • Glow plug locations on engines
  • Power must be disconnected
  • Glow plugs should be removed
  • Make sure that the plug hole and the surrounding area are clean
  • Glow plugs should be installed
  • Power supply must be reconnected
  • If you removed the valve cover previously, you should reinstall it
  • Battery negative terminal should be connected.

About Alex Harper

Alex Harper is a seasoned automotive expert with over a decade of experience in the industry. Passionate about cars and committed to sharing his knowledge, Alex combines technical expertise with a love for writing to create comprehensive and accessible car guides.

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