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Generator Surging While Not Under Load? Here’s Why

Generator Surging While Not Under Load? Here’s Why

When you think of a generator, what comes to mind? Like most people, you probably think of a large, noisy machine that powers homes and businesses during a power outage. But like most machines, generators experience problems from time to time, including surging while not under load.

If your generator is surging while not under load, it could be due to a clogged fuel filter, using the wrong fuel, low oil, dirty idle jet, or contaminated fuel. Easy fixes include cleaning or changing the fuel filter, using the correct fuel type, cleaning the idle jet, and draining the fuel tank.

You’re in the right place if you’ve been experiencing generator surging while your unit is not under load. Read on for detailed descriptions of the common causes of this problem and what you can do to fix it.

Common Causes of Generator Surging While Idle

When you think of generators, the last thing you probably want to worry about is them surging while idle. But unfortunately, this is a common issue for many generators. So what are some of the most common causes of this problem?

Here’s a rundown of the most common causes of generator surging while idle:

The Fuel Filter Is Dirty or Clogged

A dirty or clogged fuel filter is one of the most common causes of generator surging while idle. If your fuel filter is dirty or clogged, it will restrict the fuel flow to your engine, causing it to run lean. That, in turn, may cause your engine to surge.

Besides surging, a dirty or clogged fuel filter can manifest in the following ways:

  • The generator is running but not producing power.
  • The engine is sputtering or stalling.
  • Loss of power while under load.

You’re Using the Wrong Fuel Filter

If you’re using the wrong fuel filter for your generator, it can also cause surging while idle. The fuel filter is an integral part of the fuel system, and you must match it to the specific fuel type you use.

For example, you’ll need a diesel fuel filter if you’re using a diesel generator. Similarly, if you’re using a gasoline generator, you’ll need to use a gasoline fuel filter.

In addition, your fuel filter should fit the generator’s fuel line snugly. If it’s too large or too small, it can cause fuel leaks and surge.

The Oil Level Is Low

If your generator’s oil level is low, it can also cause surging while idle. That’s because the oil helps lubricate the engine, keeping it cool and reducing friction.

If the oil level is low, the engine will have to work harder, which can cause it to overheat and surge. Also, if the oil is old or dirty, it can cause the same problems (source).

The Idle Jet Is Dirty

If the idle jet is dirty, it can also cause surging while your generator is idling. The idle jet is a small passageway in the carburetor that meters the amount of fuel delivered to the engine while it’s idling.

If the idle jet is clogged, it can restrict the fuel flow to the engine, causing it to surge (source).

The Fuel Is Old or Contaminated

Another common cause of generators surging while idle is old or contaminated fuel. Over time, fuel breaks down and starts to go bad.

In addition, if your fuel tank is dirty or contaminated, it can cause the fuel to be contaminated. That can cause surging while idle.

The Weather Is Extremely Cold

Why does cold weather cause generator surging? Here are two primary reasons:

  • Cold weather can make the engine harder to start. That can cause the engine to run less efficiently, causing surging. 
  • Cold weather can also cause the fuel to thicken and clog the fuel filter. That, in turn, can restrict the fuel flow to the engine, causing it to surge.

The Carburetor Needle and Seat Are Worn

The carburetor needle and seat are two parts that work together to control fuel flow to the engine. Over time, they can become worn, causing your generator to surge while idle.

Specifically, a worn carburetor needle can cause an uncontrolled fuel flow to the engine, while a worn carburetor seat can cause a leak in the fuel system. Either one of these problems can cause your generator to surge.

The Air-Fuel Mixture Screw Is Too Tight

One of the most common causes of generator surging while idle is having the air-fuel mixture screw set too tight. The air-fuel mixture screw is located on the side of the carburetor and controls the amount of air that mixes with the fuel. 

If you tighten the air-fuel mixture screw too much, it can restrict the airflow to the engine, causing it to run lean. A lean air/fuel mixture will cause the engine to run hotter, leading to generator surging. 

The Nuts and Bolts Around the Carburetor Are Loose

Another common cause of generator surging is loose nuts and bolts around the carburetor. Over time, the vibrations from the engine can cause the nuts and bolts to loosen.

If not appropriately tightened, they can cause air leaks in the fuel system. That, in turn, can cause the engine to run lean and surge. Besides, if the carburetor is loose, it can cause the engine to run rough and surge.

The Carburetor Is Flooded

If you flooded your generator’s carburetor, it could also cause surging while idle. A flooded carburetor happens when you deliver too much fuel to the engine.

That can happen if you start the generator when it’s already running. It can also occur if you leave the fuel shut-off valve open when the engine is off. Either way, too much fuel in the carburetor can cause surging.

The Governor Is Defective or Out of Adjustment

If your generator has a governor, it’s responsible for regulating the engine’s speed. If the governor is defective or out of adjustment, it can cause surging while the generator is idling.

Specifically, if the governor is set too low, it can cause the engine to run faster than expected. That can lead to surging.

You Have an Improperly Gapped Spark Plug

Lastly, an improperly gapped spark plug can also cause a generator to surge while idle. The spark plug is responsible for igniting the fuel in the engine.

If the spark plug is not gapped correctly, it can cause the engine to misfire. That, in turn, can cause the engine to run rough and surge.

Easy Fixes for Generator Surging While Idle

Now that you know some of the most common causes of generator surging while idle let’s discuss some easy fixes. After all, once you know what’s causing the problem, it’s often easy to fix.

Here are some easy fixes for generator surging while idle:

1. Clean or Replace the Fuel Filter

One of the easiest things you can do to stop your generator from surging is to ensure you’re using the right fuel filter. By right, I mean it must be clean and compatible with your generator.

Here are a few steps to ensure you’re using the right fuel filter:

  1. First, check your generator’s manual to see what type of fuel filter it uses.
  2. Then, go to your local hardware store or generator dealer and purchase the correct fuel filter.
  3. Once you have the correct fuel filter, install it according to your generator’s manual instructions.

Note: If you’re unsure how to install the fuel filter, take it to a professional.

2. Check and Fill Oil Levels

If your generator is low on oil, it’s time to add more. Low oil levels can cause many problems, including that your generator is surging.

Here’s how to check and fill your generator’s oil level:

  1. Check your generator’s manual to see what type of oil it uses and how much you need.
  2. Locate the dipstick on your generator. It should have a handle that’s easy to grip.
  3. Next, remove the dipstick and wipe it clean with a rag.
  4. Reinsert the dipstick and pull it out.
  5. Check the oil level on the dipstick. If it’s low, add more oil until it reaches the full line.

Note: Don’t overfill your generator with oil. Too much oil can be just as bad as too little.

3. Clean the Idle Jet

As I mentioned, a dirty idle jet can cause your generator to surge while idle. Fortunately, it’s easy to clean.

Here’s how:

  1. First, remove the carburetor bowl and float assembly.
  2. Then, use a carburetor spray cleaner or compressed air to clean the idle jet.
  3. Once the idle jet is clean, reassemble the carburetor.

Note: If you’re unsure how to remove or clean the idle jet, take it to a professional.

4. Replace Old or Contaminated Fuel

If you’re using old or contaminated fuel, it’s time to get rid of it and get some fresh fuel.

Here’s how to do that:

  1. First, empty the gas tank.
  2. Then, add fresh fuel to the tank. Be sure to use fuel that’s no more than 30 days old.

Here’s a video to help you properly evacuate the old fuel:

Surging Generator? Quick repair for ALL surging and hunting engines.

5. Warm Up the Engine in Cold Weather

If it’s cold outside, it’s best to warm up your generator before using it. That way, you can avoid generator surging.

Here’s how to warm up your generator in cold weather:

  1. First, connect your generator to a power source.
  2. Then, turn on the engine and let it run for a few minutes.
  3. Once the engine is warmed up, turn on your generator’s load devices one at a time.

6. Replace the Carburetor Needle and Seat

If the carburetor needle and seat are worn, you must replace them.

Here’s how to replace the carburetor needle and seat:

  1. Remove the carburetor bowl nut with a wrench and pull off the carburetor bowl.
  2. Use a flathead screwdriver to remove the old needle and seat from the carburetor body.
  3. Install the new needle and seat in the carburetor body, ensuring they are tight.

7. Loosen the Air-Fuel Mixture Screw

If the air-fuel mixture screw is too tight, you must loosen the screw.

To loosen the air-fuel mixture screw:

  1. Find the screw on the side of the carburetor (it will have a spring next to it).
  2. Turn it counterclockwise with a flathead screwdriver until it is loose.
  3. Do not remove the screw, just turn it until it is loose.

8. Tighten All Nuts and Bolts

If the nuts and bolts around the carburetor are loose, you need to tighten them.

To tighten the nuts and bolts:

  1. Use a wrench to tighten the nuts and bolts around the carburetor.
  2. Make sure they are tight but do not over-tighten them.

9. Drain the Carburetor

If a flooded carburetor is the reason for your generator surging, you will need to drain the carburetor.

To drain the carburetor:

  1. Remove the carburetor bowl nut with a wrench and pull off the carburetor bowl.
  2. Drain the fuel from the carburetor bowl into a container.
  3. Replace the carburetor bowl and tighten the carburetor bowl nut.
  4. Start the generator and let it run until the fuel in the carburetor is used up.

10. Adjust or Replace the Governor

If the governor is defective or out of adjustment, it will need to be replaced or adjusted.

To adjust or replace the governor:

  1. Refer to the owner’s manual for your specific model of generator.
  2. Follow the instructions in the manual to adjust or replace the governor.

Caution: Replacing the governor is a complex repair that you should only attempt if you have experience working on small engines. If you are uncomfortable performing this repair, take the generator to a qualified service technician.

11. Gap the Spark Plug Properly

If the spark plug is not gapped correctly, you must remove and re-gap the plug.

To gap the spark plug:

  1. Remove the spark plug from the generator with a wrench.
  2. Clean any debris or deposits from the electrode with a wire brush.
  3. Use a feeler gauge to measure the gap between the electrode and the side of the plug.
  4. The gap should be .028-.060 inches (0.7-1.5 mm). If the gap is not within this range, use a small file to adjust it. Ensure you check the gap with the feeler gauge after each adjustment to be safe. Also, read the owner’s manual for the specific manufacturer’s recommendations on the correct spark plug gap.
  5. Re-install the spark plug in the generator and tighten it with a spark plug wrench.

Note: Call a qualified service technician to diagnose and repair your generator for the best results. Attempting repairs yourself can be dangerous and may void your warranty.

If none of these solutions work, I recommend replacing your generator with this DuroMax Dual Fuel Portable Generator from Amazon.com. It comes with dual fuel capabilities (natural gas or propane), and it has a strong reputation for being a reliable and durable generator. Plus, it’s EPA and CARB approved, making it an excellent choice for those looking for an environmentally-friendly option.

Wrap Up

If your generator is surging while not under load, it’s most likely due to one of the following issues: 

  • A dirty fuel filter
  • Using the wrong fuel filter
  • Low oil level
  • A dirty idle jet
  • Contaminated or old fuel
  • Frigid weather
  • A dirty spark plug
  • A worn carburetor needle and seat
  • An air-fuel mixture screw that is too tight
  • Loose nuts and bolts around the carburetor
  • A flooded carburetor

You can resolve most of these issues with some basic troubleshooting and maintenance. However, if you’re uncomfortable performing these repairs, take the generator to a qualified technician.

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