5 common Bad Glow Plug Relay Symptoms on 7.3 (quick fix)

The dashboard warning is the first symptom among many 7.3 bad glow plug relay symptoms. Other common symptoms of a bad glow plug relay are

Difficult Engine Start, white smoke, black smoke coming out of the exhaust, and misfiring engine.

Exposure to extreme temperatures and voltage can cause the malfunctioning of your glow plug relay. But replacing the plugs relay can help you solve the problem.

7.3 Bad Glow Plug Relay Symptoms
Bad Glow Plug Relay Symptoms chart

6 symptoms to detect  Bad Glow Plug Relay on 7.3 powerstroke

Symptoms of a 7.3 bad glow plug control module are not many. All of them are explained below.

1. Difficult Engine Start

A difficult engine start is a common sign of defective glow plugs. Malfunctioning glow plugs cause the combustion chamber to not gain the required temperature in cold weather to ignite and start the engine.

Some owners have experienced difficulty when attempting to start the 7.3 Powerstroke engine. Even with the block heater, the engine did not start at temperatures below 30 degrees Fahrenheit.

A faulty relay might be to blame if neither the fuel nor the battery is a problem.

2. Dashboard Warning

If there is an issue with your glow plugs, the plug’s dashboard light may flash. Or the check engine light may illuminate when you try to start your vehicle.

You’re undoubtedly accustomed to seeing plugs dashboard light illuminate for a few seconds when you start your car in colder-than-usual weather as the engine warms up. The first indication that anything may be amiss is if the light does not turn on or if it begins to flash.

3. Black Smoke

An imbalance in the air-fuel ratio, precisely an excess of fuel relative to the air, causes black smoke. This implies that either too much fuel is added or the fuel does not receive enough oxygen to burn.

Faulty glow plugs of the 7.3 may disturb the diesel engine’s combustion process, emitting black smoke through the vehicle’s exhaust pipe. This indicates that plugs or other crucial combustion system components are malfunctioning.

4. Decreased Fuel Efficiency

Typically, the efficiency of the fuel is not determined by the performance of plugs. Nonetheless, glow plugs do play a function in some circumstances. Diesel can be mixed with particular additives to lower the freezing point during winter, depending on the local climate.

Most likely, the blended fuel will have lower energy components and provide less fuel economy. By adjusting the engine’s operating temperature, all injected gasoline will be wholly used. Glow plugs have a contribution to the heat supply of your vehicle’s combustion chamber.

Faulty glow plugs cause the engine’s performance to deteriorate; it will also have a hard time meeting the requirements of the road. Your vehicle’s fuel economy will decrease.

You can check 7.3 Powerstroke low fuel pressure symptoms to learn more about issues related to your vehicle’s fuel.

5. White Smoke

Typically, white smoke is produced when there is insufficient heat to combust the fuel. Unburned fuel particles exit the exhaust as smoke, often emitting a strong odor from the fuel.

In cold weather, it is relatively uncommon for the exhaust to emit white smoke before the engine warms up. During engine startup, a damaged or malfunctioning glow plug causes white smoke.

6. Engine Misfiring

Combustion in diesel engines necessitates a high compression ratio, accurate timing and quantity of fuel injection, and a high compression rate. This results in diesel fuel igniting and combusting. Misfires can be caused by fuel quality, compression, and fuel injection issues.

Heat is created in the combustion chamber by compression pressure and glow plugs. For ignition to occur, a minimum temperature of 450° F / 232° C must be reached. If the vehicle’s glow plugs are defective, the chamber of the engine will not reach the necessary temperature.

Read also >> 5 Symptoms To Detect IPR Sensor Failure On 7.3 Powerstroke

How To Test Glow Plug Of 7.3 Powerstroke?

To test a glow plug control module you can use a  test light. A test light can evaluate if a glow plug relay is operating correctly.

  • Attach a test lead to the large ends of each terminal.
  • The test light should illuminate upon turning the ignition key.
  • Connect the battery to one of the two larger-sized connections.
  • The light should glow when one test lead is attached to the other big terminal, the second test lead is connected to the ground, and the ignition is turned on.

If the relay is functional, power should flow to the other end, and the relay is faulty if it does not.

What Causes 7.3 Bad Glow Plug Relay?

Plugs relay can deteriorate with time, as with most other automobile components. However, there are various causes why they may fail before their expiration date.

  • Exposure to extreme temperatures

Exposure to severe temperatures can significantly harm a glow plug. And temperatures that suddenly rise or decrease to excessive levels will cause the plugs relay to malfunction.

  • Fluctuating Electrical Currents

Using high-amperage battery chargers to “boost” start the engine is another cause of frequent glow plug problems. Many of these chargers emit an excessive voltage that can cause plugs’ tips to burst; anything that generates a voltage spike in the vehicle’s electrical circuits can damage the plugs.

  • Misfiring Injectors

The injectors of your engine might drip on plugs, causing them to degrade. Occasionally, the plugs controller can become “stuck on,” causing plugs to fail quickly. Typically, the dashboard indicator light will not illuminate when this occurs.

How Serious Is The 7.3 Bad Glow Plug Relay?

These pencil-shaped metal pieces are responsible for fast heating the engine. If the engine is not sufficiently heated for combustion, the heating element at the crown of the spark plug gets energized, thereby accelerating the process of fuel ignition.

It means the vehicle’s glow plugs are essential for the fast-starting of your vehicle.

What To Do When 7.3 Bad Glow Plug Relay Symptoms Appear?

You have to fix the problem at the plugs relay location. Replacing the bad one should fix the issue. Find the glow plugs in the engine compartment. Disconnect the wiring of the glow plugs. Take out the plugs one by one with care.

Every nut must be thoroughly cleaned. Using a reamer, enlarge the plug holes for each one. Change the plugs and tighten them using a ratchet. Using the wrench, reconnect the wires and nuts.

How Much Does It Cost To Deal With 7.3 Bad Glow Plug Relay?

Depending on quality and brand, a replacement glow plug costs between $25 and $50. Changing the plugs yourself could save you money on labor costs if you already have the proper tools.

A professional can replace your glow plugs efficiently and precisely for between $90 and $200 in labor charges.

people also ask (FAQs)

Even though you know the symptoms of a 7.3 bad glow plug, you may have some other questions regarding the plugs. Here are some frequently found queries that you may have as well.

How many glow plug relays does a 7.3 have?

Trucks made after mid-1999 will appear to have two glow plug relays. However, the front relay controls the intake air heater, and the relay in the truck’s rear compartment controls plugs. This relay is the replacement for all types and years of Powerstroke trucks.

Are glow plugs only used for starting?

Plugs are used exclusively to start engines of this size. Due to the catalytic impact of the platinum wire on the methanol-based fuel developed for use in model engines, glow plugs are an essential component of the ignition system.

Do glow plugs stay on after the light goes out?

Even if the engine runs during the post-heating period, plugs will remain lit. The length of the post-heating phase depends on the kind and temperature of the engine. For this purpose, only glow plugs with “post-heating” are utilized.

7.3L Powerstroke Cold No Start Diagnosis- Glow Plug Relay >> Check out the video below:

Take away

The 7.3 bad glow plug relay symptoms will assist you in determining if your glow plug relay needs to be replaced or not. Replacing plugs is the best course of action for your car, and it is better to bring in an expert to resolve the issue.

Although this is costly, it will be better for your vehicle in the long run. If you avoid exposing your car to high temperatures or voltages, plugs relays should last long.

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Mahir Ahmed


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