How to Change Spark Plugs in A Generator

A spark plug is an essential part of a generator that can quickly wear out if not well-maintained. The value is its ability to generate a spark that ignites the gas to burn.

However, a faulty spark plug can cause a generator to underperform or, in the worst-case scenario, cause it to burst into flames or explode due to overheating. In such instances, it is necessary to replace a failed spark plug with a new one.

Learning how to change spark plugs in a generator is a fairly straightforward process. You can get by with very little specialized training, and the steps involved are fairly basic.

That’s why this post will provide step-by-step instructions that should enable even a novice to change out an old spark plug for a new one with relative simplicity.

What is Spark Plug?

These electromechanical devices, sometimes known as ignition coils, are crucial for internal combustion engines. They produce sparks that ignite air and fuel mixtures, resulting in power generation from burning gases.

How Do They Work In a Generator

The spark plug in a generator works similarly to regular spark plugs in cars. In simple words, inside of a spark plug, you’ll find two electrodes: a center electrode and an outer electrode.

When an electric current is applied across an ignition coil of a spark plug, it creates a high voltage pulse. These pulses then move through the air and ignite gas or liquid fuel inside an engine, thus resulting in combustion and generation of power.

However, spark plugs tend to degrade with time and require replacement every 60-100 hours, depending on usage.

Key Features to Look Out For When Shopping For a Spark Plug

1. Material

The first thing you should check is whether or not your spark plug is constructed of wear-resistant material.

Most lower-quality plugs are made of cheap metal alloys and other materials that can erode quickly, causing efficiency issues with your engine. To ensure you’re purchasing a quality product, opt for plugs made from copper or platinum-iridium. However, copper tends to be one of the more expensive materials.

Fortunately, some companies offer options like a platinum core surrounded by copper alloy material—which means you get excellent performance without breaking your budget.

2. Full thread depth

Some spark plugs only penetrate down into cylinders by half of their length. Not surprisingly, these spark plugs are harder to install and have a much higher rate of misfires. Some even cause damage in extreme cases.

You can easily spot if your spark plug doesn’t go deep enough; all you need is a regular screwdriver or a ratchet wrench that goes down deep enough into your cylinder head. If you feel some resistance at around two inches, your plug is probably fine.

Remember to always get your spark plugs from a reliable source that sells full thread-depth plugs; it’s an investment you won’t regret.

3. Gap style

This measurement is given in thousands of an inch, and it tells you how much space exists between two electrodes inside a spark plug.

If there’s too little space, your engine will run roughly; if there’s too much, it may cause misfires and stalling. An improper gap size can also lead to excessive heat or weak ignition.

The best way to measure an appropriate gap size is using an air gauge. If you don’t have one, you should find guidelines in your generator’s service manual.

4. Ground electrode location

The ground electrode is typically located on top of or in front of the spark plug body and may be visible when looking down into it.

The location is important because it dictates how easily you’ll be able to reach inside your engine compartment to remove and install a new plug. If it is difficult to access, it means you’ll have limited options if it fails during a power outage.

So, ensure that any spark plug you choose has easy-to-reach electrodes by reading online reviews before making your purchase.

5. Size

Spark plugs can be found in many different sizes, so ensure you purchase one that fits your generator’s engine. An incorrectly sized spark plug leads to slow fuel combustion, which forces your engine to burn more fuel than necessary. In addition, it causes a hard start to your generator since little or no power reaches your engine’s cylinders.

The correct plug size is typically printed on your generator’s engine. Alternatively, check with a mechanic or consult your owner’s manual.

A Step By Step Guide on How to Change Spark Plugs in A Generator

Tools and Materials Needed


  • Work gloves


  • A thick shirt (protection from oil)


  • Flathead screwdriver

How to Change Spark Plugs in A Generator

  • Spark plug socket

How to Change Spark Plugs in A Generator

  • A set of new spark plugs

Step 1 – Turn Off and Unplug All Power Cords

Before you can change your spark plugs, ensure that your generator is turned off and all power cords unplugged. This protects you from electrocution and unintentional shorting out of sensitive engine components and damaging your plug-in.

Step 2 – Locate the Spark Plug

Your spark plug is normally located in or near your engine compartment. Often, it will be under a removable access panel or on top of a rubber/vinyl tube that covers up part of your engine.

The exact physical location will vary based on the make, model, year, and size of your specific generator. If you are unsure how to find it, refer to your owner’s manual. Once found, move on to step two.

Step 3 – Remove Spark Plug Boot and Separate Wire Harness Connector

Now that you have located your specific generator’s spark plug, we can take it out.

To do so, pull off the plug boot surrounding your plug and then unplug them from where they connect to their power source. Next, disconnect all wires from the housing by loosening them with a wrench or pliers.

Also, remove any dirt or debris around the spark plug with a wire brush and compressed air, if necessary.

Step 4 – Unbolt and Remove the Old Spark Plug

Now that everything is safe and disconnected go ahead and remove your generator’s old spark plug.

Use the spark plug socket to loosen and remove the spark plug by turning counterclockwise (one-quarter turn). Next, twist off and remove your old spark plug by hand.

Finally, if necessary, wipe off excess grease or debris around the spark plug with a wire brush and compressed air.

Step 5 – Examine the New Spark Plug

Once your previous spark plugs have been successfully removed, take some time to examine your new replacement for signs of wear or build-up on its tip. If there is any such grime present upon closer inspection, try wiping it away before proceeding with reinstalling everything else.

Step 6 – Install the new Spark Plug

Follow instructions supplied with your replacement spark plugs to install, tighten and torque down one properly.

To do so, use a wrench to twist your new spark plugs tightly into place without exceeding any higher torque limits than necessary. As you probably already know, too much torque could ruin your entire connection entirely.

Step 7 – Reconnect Wire Harness Connector and Reinstall Plug Boot

As soon as you finish tightening up your new spark plugs, reconnect the two wires previously disconnected using hands and a small flathead screwdriver. Finally, slide over the plug boot back onto its original position. Make sure that everything is fastened securely before continuing onto the next step.

Final Step – Test

Now that your brand new spark plugs are in place head back to your generator’s main power switch and flip it on to make sure everything works as expected.

Faqs About How To Change Generator Spark Plugs

1. When should I replace my generator spark plugs?

You should replace spark plugs after every 100 hours of operation. When you do so regularly, your generator will start and function smoothly. Spark plugs that are too old or worn-out might reduce performance and cause engine damage over time.

2. How do you remove a spark plug from a portable generator?

First, turn off your generator and unplug all the power cords. Next, using a 3/8-inch wrench or socket, remove each of the two nuts holding it on, then pull off the wire that connects to it. Once you’ve got it loose, pull out your old spark plug.

3. How do you tell if a spark plug is bad in a generator?

If the generator takes a long time to start or won’t start at all, and runs roughly. In addition, if your generator’s fuel consumption has increased compared to the previous usage.

4. Where is the spark plug located in a generator?

The spark plug is located at an angle on top of the generator covered with a spark guard. This spark guard helps protect against any foreign particles that could be causing sparks, therefore preventing damage and wear to your generator’s internal parts.

5. Does a generator have a spark plug?

Yes, all generators have a spark plug. The spark plug ignites the gas to produce electricity in homes. Without it, generators wouldn’t function properly.

6. What spark plug does a generator use?

A generator uses a spark plug with a gap size of 0.031 inches at most. Most generators use Platinum tipped plugs, which can handle high heat and compression levels within the engine during regular usage.

7. What is a spark plug gap?

How to Change Spark Plugs in A GeneratorA spark plug gap is an adjustable distance between two electrodes within or on a spark plug. It’s designed to help determine how far current travels from one electrode to another inside a cylinder during ignition.

8. Why is my generator killing plugs?

There are several reasons why your generator is destroying plugs. These include Low-quality fuel or oil, a dirty air filter, water-damaged spark ignition coils, and high voltage or current caused by a poorly placed choke.

9. Are all generator plugs the same?

Generators have different-sized spark plugs, so you need to determine your generator’s voltage and size before purchasing a new one. Consult your owner’s manual for information on what size and type of plug your generator uses, as well as for any special instructions for changing it out yourself.

10. Can you repair spark plug wires?

Yes. If your spark plug wires are torn or frayed, you can replace them with new ones. However, if they’re severely damaged, they may have to be cut out and replaced completely.

Closing Thoughts

As seen in the post, as your spark plugs age, they become dirty, which means your generator may not be getting as much power as it used to.

And while having a dirty set of spark plugs isn’t going to stop your generator from working entirely, you may notice a decrease in performance. If you experience such problems with your generator, diagnosing whether or not it’s a problem with spark plugs might save you time and money on parts.

Finally, following the steps mentioned above will ensure you change your spark plugs safely, effectively, and efficiently.

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About Steve Stuart

Steve Stuart is an electrical engineer who developed interest on generators during his school years. After school, he became a generator enthusiast. This is after encountering power supply problems at the area of residence where he lived. Power would be on and off and so food would go bad and the room heater would go off especially during winter. After trying the different generator brands for several years, Steve now provides information on the available brands and products in the market today. Based on his experience, he gives the do’s and the don’ts when it comes to generator use.

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