HOW DO GLOW PLUGS WORK?

No matter how you look at it, car technology has come on leaps and bounds

over the past decades. And, while some of these advances are immediately noticeable and

appreciated, such as electric windows and smoother suspension systems, others, like glow

plugs, are hidden under the bonnet and forgotten about unless something goes wrong. This

shouldn’t be the case. Heat glow plug

technology has significantly improved, with BERU, for example, dramatically

improving the time it takes to start your diesel car – especially on cold mornings.

So, let’s appreciate the hidden and take a look at BERU glow plugs – what

are they, the different types available and how they compare to the competition.
What is a glow plug?

To get started, we need to go back to basics: what is a glow plug? And,

what does a glow plug do?

A glow plug is a heating element that heats incoming fuel and air to

encourage efficient fuel combustion in a diesel engine. The fuel combustion starts your

engine so that you can drive. Each cylinder of your engine has one glow plug, either in the

pre-chamber (pre-chambered engines) or in the combustion chamber (direct-injection

engines).

GLOW PLUG SYSTEMS

The starting process of an engine heavily influences the exhaust gas values

of a vehicle. Together, glow plugs and their connected components (glow plug control

modules, glow plug relays and glow plug combustion sensors) play an important role in

reducing emissions helping to protect the environment.
Glow plug is specialized heating

devices used to aid in the starting of diesel engines. They are similar to spark plugs in

design; however, they differ in their primary function. Instead of producing a timed spark

to ignite the fuel mixture, like spark plugs do, glow plugs simply serve to produce

additional heat that aids the diesel engine combustion process during cold starts.

Diesel engines rely entirely on the heat generated by cylinder compression

to ignite the fuel mixture. When glow plugs begin to fail, this additional heat that

aids the combustion process is gone, and the engine may become more difficult to start,

especially in cold weather.

Another symptom of faulty glow plugs is black smoke being

observed during start up, indicating the presence of unburned fuel due to an incomplete

combustion process. In this guide, we will cover how to test the resistance of glow plugs

to determine if they are functioning properly.

Part 1 of 1: Testing your glow plugs

tep 1: Determine the multimeter’s resistance value. Before testing the

terminals, you must determine the resistance value of your digital multimeter. To do this,

turn the multimeter on, and set it to read in Ohms.

Once the multimeter is set to read in Ohms, touch the two leads of the

multimeter together and examine the resistance reading that is displayed.

If the multimeter reads zero, try changing the setting of the multimeter to

a higher sensitivity until a reading is obtained.

Record this value on a piece of paper, as this will be an important value

in calculating the resistance of your glow plugs later on.

Step 2: Locate the glow plugs in your engine. Most glow plugs are installed

in the cylinder heads and will have a heavy gauge wire, similar to a regular spark plug

wire, attached to them.

Remove any covers that may be obstructing access to the glow plugs, and use

the flashlight for additional illumination if necessary.

Step 3: Disconnect the glow plug wires. Once all of the glow plugs have

been located, disconnect any wires or caps attached to them.

Step 4: Touch the negative terminal. Take your multimeter and touch the

negative leads to the negative terminal on your vehicle’s battery.

If possible, secure the lead to the terminal by tucking it inside or

underneath the clamping mechanism of the post.

Step 5: Touch the positive terminal. Take the positive lead of your

multimeter and touch it to the terminal on your Mitsubishi glow plugs.

Step 6: Record the glow plug’s resistance. With both leads touching the

terminals, record the resistance reading that is indicated on the multimeter.

Again, the reading that you get should be measured in Ohms (Ω).

If no reading is obtained when you touch the glow plug, make sure that the

negative lead is still in contact with the negative battery terminal.

Step 7: Calculate the resistance value. Calculate the true resistance value

of the glow plug by subtracting.

The true resistance value of the glow plug can be determined by taking the

resistance value of your multimeter (recorded in Step 2) and subtracting it from your glow

plug resistance value (recorded in Step 6).

Step 8: Evaluate the resistance value. Compare your calculated true

resistance value of your glow plug with the factory specification.

If the glow plug resistance exceeds the specification or falls out of the

acceptable range, then the glow plug must be replaced.

Step 9: Repeat for other glow plugs. Repeat the procedure for the remaining

glow plugs, until they have all been tested.

If any of the glow plugs fail the test, it is recommended that the entire

set be replaced.
Replacing just one, or a few, of the glow plugs may cause engine problems

similar to a faulty glow plug if the resistance readings are too far apart.

For most vehicles testing the resistance of a glow plug is a pretty simple

procedure, granted the glow plugs are in an accessible location. However if they are not,

or this task is not something that you feel comfortable taking up on your own, this is a

service that any professional technician, such as one from YourMechanic, should be able to

perform quickly and easily. If necessary, they can also replace your

Isuzu Glow Plugs

 so that you can start your car like normal.

There are very few glow plugs that are considered universal plugs

(OS' #8 plug is an example). For the most part, the type of fuel you are running will

impact the kind of glow plug you need to use. Another component in the nitro fuel is

nitromethane. The Nitro Percentage of your fuel determines the ignition point as well; in

other words, the more nitro you run, the more you advance the ignition point. Ideally, the

ignition point will be when the engine is at top dead center (TDC). This will force the

piston down and back up again for another stroke. But when you run higher nitro content and

don't switch to a colder plug, you will advance the ignition point and result in less-

than-optimum performance, since the piston is still on its compression stroke (the upward

stroke) when the air/fuel mixture is ignited.

In general, the higher the the nitro percentage, the colder

the plug should be. Conversely, the lower the nitro percentage, the hotter the plug should

be.
Glow plugs are an engine management component that is found on

vehicles equipped with diesel engines. Their purpose is to preheat, and help warm up the

engine’s cylinders so that diesel combustion can occur more easily. They play an

especially important part in warming the vehicle’s cylinders during cold starts, where

starting the engine is most difficult. Glow plugs use an electrode which will warm up and

glow orange when current is applied. When the glow plugs have an issue, they can

usually cause problems with the driveability of the vehicle. Usually bad or failing

glow plugs will produce a few symptoms that can alert the driver of a potential issue.

1. Engine misfires or decrease in power and acceleration

Engine misfires are one of the first symptoms of an issue with

the vehicle’s glow plugs. If the Mazda Glow Plugs malfunction they will not provide the additional heat

that aids in diesel combustion, which may cause the engine to experience misfires. The

misfires may cause a loss in power, acceleration, and even fuel efficiency.

2. Hard starting
Another symptom of an issue with the vehicle’s glow plugs

is hard starting. Unlike gasoline engines, which use a spark to ignite the fuel

mixture, diesel engines rely solely on cylinder pressures to ignite the diesel fuel

mixture. If the glow plugs fail, the engine will have to overcome additional pressure in

order to ignite the mixture, which may result in hard starting.

3. Black smoke from the exhaust

Another symptom of an issue with the glow plugs is black smoke from

the exhaust. Faulty glow plugs may disturb the sensitive diesel combustion process, which

may cause the engine to produce black smoke from the tailpipe. Black smoke can also be

caused by a wide variety of other issues, so having the engine properly

diagnosed is highly recommended.

Glow plugs are found on virtually all diesel engines, and play an

important role in starting and operating the engine. If your vehicle is displaying any of

the symptoms above, or you suspect that your glow plugs may be having an issue, have the

vehicle inspected by a professional technician, such as one from yourMechanic,

to determine if the glow plugs need to be replaced.

Continuous Improvement

The diesel engine is continuously being improved, in terms of its

fuel consumption, power outputs and, ultimately, refinement. Drivers of modern diesel

vehicles expect to be able to just jump in, turn the key and go. It’s no longer acceptable

to have to wait 8 to 10 seconds for a glow plug light to go out before you can start the

engine. One of the reasons this is possible is because of the technical advances that have

been made in glow plug design, in particular with the development of both twincoil

technology and the latest third generation of glow plug – the New High Temperature Ceramic

type, or NHTC. In this article we take a closer look at these latest types of plugs in more

detail; the manufacturers spearheading the new technologies, and the major motor

manufacturers adopting them as OE.

Twin -coil Technology

Using twin-coil technology, Toyota Glow Plugs can be made to heat more quickly and

then self-stabilise at the correct temperature. This type of plug is more resistant to

misuse, as it will prevent overheating of the main coil and allows longer post glow

periods, giving cleaner exhaust emissions.

Each twin-coil glow plug has been designed and tested to 7,000

heating cycles before being approved for production. This means that if the engine is

started from cold twice per day, the glow plug could have a life expectancy of 10 years or

more.

Glow plugs are probably far more intricate than you may imagine

them to be. It takes precision laser welding to join the heating coils, which are then

tested for maximum temperature and rate of temperature rise. This is to ensure that the

glow plugs reach 850°C within a specified time.