How Do Glow Plugs Work In A Diesel Engine?

Glow plugs work similarly to small heaters on your car’s hood. They warm the air and diesel in your engine as heating elements, allowing for efficient combustion.

Glow plugs work in the same way that spark plugs do. However, instead of sparking the ignition in petrol engines, they heat the air and fuel in diesel engines to ignite them.

Every cylinder in a diesel engine has a glow plug, which is why different types and models require different numbers of glow plugs.

Are glow plugs only used for starting?

Model engine glow plugs are not the same as those found in full-size diesel engines. Only the glow plug is used to start full-size engines. Because of the catalytic impact of the platinum wire on the methanol-base fuel they are supposed to run on, model engines employ glow plugs as an essential part of the ignition system.

In theatrical pyrotechnics and the special effects industry, model engine glow plugs are also employed as re-usable igniters to remotely ignite pyrotechnic devices using flash and smoke composition powders.

How do diesel glow plugs work?

Because of the comparatively high temperature of the intake air and the relatively low ignition temperature of diesel, it is feasible to start a warm diesel engine without utilizing a glow plug or in warm climates. This, however, is insufficient to assure effective ignition of the injected fuel at all temperatures, resulting in higher exhaust emissions. This problem is solved by using a glow plug. It’s an electrical heating device in each cylinder of a diesel engine that ensures reliable starts in any weather.

What does a glow plug look like?

A glow plug is a long, thin metal item having a heating element at one end. The heating element is made of oxidation-resistant materials that can withstand high temperatures.

How does a glow plug work?

Unlike a spark plug, which is required at all times while driving, a glow plug is only required during the ignition process. The glow plug heats up and emits visible light by energizing the heating element (hence the name). Before the fuel injector spray directs fuel onto the hot tip of the glow plug during the injection of the fuel, the intake air is compressed. Even when the engine is cold, the injected gasoline mixes with the compressed air, evaporates, and begins burning practically instantly.

Will a diesel start without glow plugs?

Glow plugs are frequently used as a starting assistance for engines. Many designs without glow plugs still exist today (military diesels, for example), and even modern diesel engines can be started even if the glow plugs fail (unless the onboard computer prevents it).

Do glow plugs work when engine is warm?

Glow plugs, unlike spark plugs, must be sufficiently warm under pressure to self-combust. Fuel requires little aid from other automotive parts to achieve this in hot conditions. Diesel engines, on the other hand, have a hard time igniting gasoline in cold temperatures. In order for the engine to start, the glow plugs heat the fuel.

The intake air is compressed to start the engine, and when the piston rises, the engine injects diesel into the combustion chamber. The injected fuel reacts with the oxygen in the air, evaporating and igniting.

These steps are almost synchronous since the ignition occurs so fast after evaporation.

What happens if glow plugs fail?

Fuel efficiency is usually determined by temperature and fuel, not glow plug performance. Glow plugs, on the other hand, do have a place in specific situations.

During the cold months, diesel may be combined with appropriate additives based on the local climate to lower its freezing point. The combined fuel will almost certainly be lower in energy and deliver lower fuel economy. To guarantee that all of the injected gasoline is thoroughly burned, the engine’s operating temperatures should be regulated. Glow plugs contribute to the extra heat in the combustion chamber.

The engine’s performance will be harmed if the required temperature is not attained owing to malfunctioning glow plugs, and it will have to work harder to satisfy the demands of the road. The vehicle’s fuel efficiency will suffer as a result.

If the car exhibits any of the other symptoms indicated below, as well as lower fuel efficiency, it should be sent to an authorized workshop as soon as possible for a proper diagnosis and treatment.

What causes glow plugs to fail?

Several issues with diesel glow plugs can occur. Excessive heat or high voltages reaching the plug are the most common causes of glow plug failure. A controller that is beginning to fail can result in high voltage. Furthermore, if there is bad wiring or a controller malfunction, the glow plug(s) may receive electricity all of the time. The plugs will burn out prematurely because they are not supposed to be on all of the time. Excessive heat might also be produced by the timing of the engine or fuel leaking from the injectors (s). Running the engine with gasoline will, of course, destroy the glow plug tips owing to heat buildup in the pre-chamber.

Do glow plugs affect idle?

The dashboard’s engine warning light is frequently the first indication that something is wrong. Vehicles with this light should be taken to an authorized workshop as soon as possible for a full diagnosis and service. The engine warning light might come on for a variety of reasons; we’ve outlined the signs that indicate to damaged glow plugs below.

1. A difficult start

The most common sign of damaged glow plugs is a difficult start. Without properly functioning glow plugs, the combustion chamber may not reach the proper temperature to ignite the gasoline and start the engine in cold temperatures. Glow plugs should be checked if there are no problems with the gasoline or the battery.

2. Misfiring of the engine

In diesel engines, the combustion process necessitates a high rate of compression, as well as fuel supplied at the right moment and in the right volume. The diesel fuel is ignited, resulting in combustion. Fuel quality, compression, and fuel injection difficulties can all lead to misfires.

Compression pressure and glow plug heat provide heat to the combustion chamber. For ignition to occur, it must reach a temperature of at least 450° F / 232° C. The engine chamber will not attain the requisite temperatures if the glow plugs are defective.

3. Idling in a rough manner

If one or more glow plugs have burned out, become carbon fouled, or have been damaged, the engine will become increasingly difficult to start as the temperature drops, and it will idle rough and emit white smoke from the exhaust for many minutes once it does start. Check the fuel injection timing if all of the glow plugs are burned at the tips.

4. A reduction in fuel efficiency

5. Smoke that is white

When there isn’t enough heat to burn the fuel, white smoke appears. Unburned gasoline particles escape out the tailpipe as smoke, giving off a strong fuel odor. During cold weather, white smoke from the exhaust is common until the engine has warmed up.

When an engine starts up, white smoke might be caused by damaged glow plugs or a malfunctioning glow plug control module. Low engine cranking speed, low compression, and air in the fuel system are all probable reasons of an excessive amount of white smoke. If white smoke persists after the engine has warmed up, the problem could be one or more defective injectors, delayed injection timing, or a damaged injection pump.

6. Smoke that is black in color

An imbalance in the air-fuel ratio – too much fuel and not enough air – causes black smoke. This indicates that either too much fuel is being added to the mix or not enough oxygen is being given to allow the fuel to burn. Faulty glow plugs can disrupt the delicate diesel combustion process, causing the engine to produce black smoke from the exhaust pipe. This is a warning indicator that something is wrong with the glow plugs or other important combustion components.

DENSO has been a leader in OEM automobile technology for a long time. As the world’s leading automotive component producer, we continue to invest in R&D to assist the world’s top automakers create vehicles that are more responsive, efficient, and reliable.

DENSO Aftermarket offers OEM-quality glow plugs for all makes and models. DENSO Glow Plugs provide a wide range of options, from excellent start-up performance to longer post-heating temperatures. All contemporary glow plug technologies are covered in the program, including single coil, double coil, extended post-heating, ceramic, and immediate heating.