Why Is My Generator Backfiring? 6 Easy Fix!

“Why is my generator backfiring?” is one of the most common questions I often get asked. If you’re generator is making popping noises and throwing fire blasts during ignition, no need to get worried. This is called a “backfire” and it can happen for many reasons.

Generators backfire when there is a combustion of unburnt fuel exiting the exhaust. It is a timing issue where the ignition delays, and fuel is ignited as soon as it leaves the exhaust valve.

However, there are several other reasons for a generator backfire. There are chances the generator has not been used in ages. The fuel might be excess, low, too old, or clogged fuel lines. Fortunately, all these problems have some easy fix to some extent.

Let’s dive right in and see the causes of a generator’s backfire and how to fix them.

Why Is My Generator Backfiring?

Several reasons might make a generator backfire. Understanding the cause can help you fix the problem and avoid further damage to the generator.

Why Is My Generator Backfiring

Here are major causes of generator backfiring:

1. Incorrect engine timing

Delayed timing in the engine can cause a backfire. Once you start your generator, the engine ought to start right away. However, the ignition cycle might start late.

This ignites the fuel in the exhaust valve as soon as it opens instead of waiting for it to be fully open. Ideally, when you start a generator, the piston moves down and pulls in fresh air and fuel. The valve should shut as the piston compresses.

When there is delayed ignition, a spark ignites the mixture and causes a backfire in the carburetor.

2. Lean Air-Fuel Mixture

Next, running a generator with a lean air-fuel ratio causes slow combustion and can also cause a backfire. The combustion process in the combustion chamber should end when the piston is on a power stroke.

If the piston cycles back while the combustion process is going on, it expels unburnt fuel through the exhaust pipe. This also causes a generator to backfire.

Generator engines can run lean air-fuel mixtures when jets are restricted or when leaks occur in the gasket.

3. Low oil levels

How often do you check the oil levels in your generator? This is the first thing you need to check when setting up a generator. Low oil levels can make a generator backfire.

The generator needs a good amount of oil to start and run properly. You can always check the oil level by pulling the dipstick when the generator is placed on an even surface.

4. Low/Old Fuel

A generator backfire can also occur when the generator is low on fuel or has old gas inside. Check the fuel gauge and see the fuel level. In addition, fuel that has sat in the generator for months degrades over time.

Fuel that is a few months old becomes cloudy and starts to separate. While the fuel gauge might read sufficient, the fuel inside might not be of use. This will affect the overall performance of the generator and may cause backfires.

5. Open Choke Valve

When a generator starts internal combustion, the choke valve should be closed. The valve restricts airflow inside the combustion before you start the engine.

Ideally, the engine requires more fuel to air ratio to start easily. The choke ought to be opened once the engine is up and running.

However, if you leave the choke open, the engine gets more air than fuel and prevents it from starting.

pHow To Ensure Your Generator Always Has Gas

6. Closed Fuel Valve

Just as the choke valve regulates air flow, the fuel valve controls the amount of fuel from the fuel tank to the combustion chamber.

If the fuel chamber is closed, the combustion chamber will not get enough fuel to start. Instead, the generator will sputter, and any attempt to start it will cause a backfire.

7. Clogged Fuel Line

Anything that affects the fuel line will also prevent your generator from starting and cause a backfire.  If the fuel line is clogged, leaking, or pinched, it can affect the amount of gas getting into the combustion chamber.

Subsequently, this prevents the generator from starting causing a backfire. Make sure to replace damaged, leaking, or clogged fuel lines.

8. Bad Spark

A bad spark can also cause a backfire by delayed ignition. A spark ignites the compressed fuel and starts the generator engine. If the spark is bad, the combustion system will not ignite as it lacks a spark. This leads to timing issues and backfiring.

Can a Backfire Damage a Generator’s Engine?

Backfires can damage a generator’s engine, cause fires, power losses, and poor fuel consumption. You should never assume a generator backfires. The sounds are generally loud and can even scare neighbors.

If left unchecked, backfires can damage your generator exhaust fuel intake. In addition, a backfire means your generator is not getting enough power as normal. This leads to increased fuel consumption.

Can a Backfire Damage a Generator’s Engine

You need to pay attention to any backfires to prevent engine damage. If the problem is not fixed early, it can lead to further damage and costly repairs.

This is important, especially for campers that solely depend on generator power. A generator to power a pop up camper should have regular maintenance to avoid unnecessary power losses.

How Do You Fix A Backfire On A Generator?

You can fix a backfire on a generator by identifying the cause of the backfires and taking the necessary steps to stop it. There is no single method of fixing a backfiring generator. How you fix it depends on the exact cause of the backfire.

Typically, the first step is to diagnose the generator and identify what caused the backfire. For example, a generator that backfires due to low or excess oil can be fixed by putting the right fuel levels.

Most generator backfires that start when starting the engine usually need fixing. However, if a generator backfires when changing from a high RPM to a low RPM when switching off might not need fixing.

Here are a few steps to fixing a backfiring generator.

1. Check for Low Oil Levels:

Check the oil level and refer to the manufacturer’s manual to meet the correct levels. Here is a video on how to correctly change a generator oil.

2. Replace Old Fuel:

If the fuel is low or old, then check the fuel gauge and the right amount of fuel. Old oil should be siphoned, and fresh oil added.

3. Close Choke Valve Before Starting:

Make sure you close the choke valve before starting the engine. You can then open it when the generator is running.

4. Clear Clogged/Damaged Fuel Line:

Flushing the gas tank and fuel line can unclog the fuel lines. If the fuel lines are excessively damaged, consider replacing them.

5. Open Fuel Valve:

Make sure the fuel valve is open before starting the engine. You need fuel flowing to proper channels to start the engine.

6. Bad Spark Plug:

Is there any debris on the spark plug? If yes, consider cleaning it. Before cleaning the spark, ensure the generator is shut off, and the turn-on switch is off. Next, remove any cables connecting the spark and remove them.

Use a socket wrench to loosen and then eventually remove the spark plug. You can then inspect the unit and see if it needs a replacement or just cleaning. Use the generator fuel to clean it.

Final Verdict

A generator backfiring and not starting can come as a surprise. However, the reasons are quite simple and easy to fix. First, make sure the generator is set up properly. Next, check the oil levels, fuel levels, choke valves, and fuel valves.

You need to limit airflow before starting and ensure there is a higher fuel quantity. The choke valve can be open afterward. In addition, check the spark plug, fuel lines and ensure everything is correct.

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