9 Reasons a Gas Generator Won’t Start (And How To Fix)

Many things in this world will have you banging on the nearest wall and swear to take revenge on inanimate objects. One of the biggest ones is when everything is perfect for the generator, yet it still won’t start.

Some common reasons a generator won’t start are low fuel, low oil, or too much power draw. If all of those things are not an issue, you may need to adjust the choke, clean the air filter, or check the spark plugs. Your generator may also be flooded, have carburetor problems, or have battery issues.

Each mistake you need to understand will affect your generator differently, requiring that you either take a few minutes to fix it or start a complete service. Before you can fix each problem, you need to understand how each fault can happen and adequately address them.

Why Your Generator Won’t Start and How to Fix It

There are many reasons why your generator won’t start, and it’s because you usually make a simple mistake or forgot to check on a few essential things. Many first-time generator owners forget to check on some parts, cause some problems, or even just causing the system to be damaged.

Each generator, as they age, will experience each problem, with a lot of people learning that it is only natural that you need to fix these parts. Most of the time, these faults can be fixed within a few minutes, while others can require that you do a bit of work to ensure that everything is going well for your generator.

Here are some of the most common reasons why your generator won’t start:

  • Low Fuel
  • Low Oil
  • Power Draw
  • Choke Adjustment
  • Air Filter
  • Spark Plug
  • Carburetor
  • Flooded
  • Power Problem

Knowing what can cause your generator not to work correctly or entirely fail to start is only half the battle; you will need to know what to do to fix these issues. Some of them can be pretty simple and should be a part of your regular maintenance, while others are things that you have to check every few months.

Each part of the generator requires different ways of fixing them, with each one allowing your machine to start up quickly. Many people get comfortable with their generators and forget to do all the proper maintenance, and then their machine breaks down, and they act surprised.

Let’s look at some of the most common reasons a generator won’t start and discuss how to fix each problem.

1. Low Fuel

It is not as odd or evident as it may seem; many times, the fuel in a generator ran out while you were using it previously. Many people mistakenly stop using their generator just before it runs dry, which causes them to think the generator will be exemplary the next time they need it.

How to Fix Low Fuel In a Generator

Check the fuel levels before you start the generator, and always be sure to start with that before checking other parts of the system when not starting. You can use the fuel in a generator a lot faster than you could imagine, and many times it is why your generator won’t start.

2. Low Oil

Low oil in a generator can cause a lot of damage to the internal parts of your generator. Most modern generators have automatic sensors that will stop the machine from running when there is insufficient oil.

How to Fix Low Oil In Your Generator

Replacing the oil will take a few minutes of unbolting, catching, and fixing. It is best to have all your tools ready to go when you replace the oil in your generator to ensure everything goes smoothly. Generators are pretty heavy on their oil as the machines run hot, requiring that you ensure the oil is always filled and clean.

3. Power Draw

One of the most common reasons a generator won’t start is if there is too much draw from the generator. The electrical equipment that draws power from the machine sucks up all the energy that should be going into starting the engine.

How to Fix a Generator Power Draw Problem

If you have constant issues starting the machine, it is best to have it entirely unplugged; any unwanted draw on the generator will cause it to have difficulty starting. It should only take a few seconds to unplug everything, and the generator will quickly start.

4. Choke Adjustment

The choke is tricky to have on your generator; adjusting it requires finesse and knowing what to do right. Most of the time, people have the choke too closed or too open, which causes a list of other problems as unspent fuel fills the entire system.

How to Adjust the Choke On a Generator

Along with checking the available fuel, you should adjust the choke, especially if it feels and sounds like the machine has a lot of water flowing through it. You can hear when the compression fills with fuel, and no combustion occurs; the only solution is to adjust the choke and start the engine until it turns over.

5. Air Filter

If the air filter is dirty, there won’t be air in the engine to start everything, causing the entire combustion process to fail. Usually, people assume that it should be fine as long as the air filter isn’t covered. However, a dirty air filter can cause as many if not more problems.

How to Fix the Air Filter On a Generator

Replacing filters is what you should be doing at least once a month if you use the system often. New air filters, new petrol filters, and a new oil filter will cause your generator to run like it is brand new as it breathes many breaths of fresh air.

6. Spark Plug

Spart plugs can last a long time, but they are not like diamonds; they don’t last forever, and you must check them to ensure they’re fine. As the spark plugs deteriorate, the longer the system starts and the more inefficient it becomes.

How to Fix Generator Spark Plugs

To check the plugs, remove them from the housing, leave them plugged in, and start the machine. If there is no spark or the gap is too large, you should replace the sparks as it is a clear sign that the spark plugs have gotten too old to be used properly.

7. Carburetor

The part where the fuel and the air mix together before heading into the pistons; most if not all generators use them. If left for a few months, the carburetor will become clogged and gunky thanks to the fuel left inside.

How to Fix the Carburetor On a Generator

If your generator has been standing for a long time, you must check and clean out the carburetor. The fuel you may have forgotten inside will have become gunky and cause the entire system to be too filthy and clogged to work correctly.

8. Flooded

Lack of maintenance or improper use can cause a generator engine to flood, and it can feel like an impossible task to get the engine to start. Flooding occurs when there is only gas inside the pistons with no air mixing to cause proper combustion.

How to Fix a Flooded Generator

If the system is not starting with the choke applied, it means the system is wholly or partially flooded, you must open the choke to let it run normally. You are trying to start the system with the choke open to remove the excess fuel, with the last little bit most likely causing the system to start.

9. Power Problem

Depending on the age of your generator, you will have a battery problem when you start the engine. Even if you have a pull start motor, if the generator’s battery does not work correctly, you will face a big challenge as the machine will not start.

How to Fix a Generator With a Power Problem

The battery not providing enough power means that you should replace it; unlike cars, the power from the battery won’t drip. Once a generator’s battery has died, you can either charge it or replace it with a new one. Generator batteries are usually relatively small and inexpensive.

Underlying Issues That Cause Generators To Not Start

We now know how to fix each problem and what exactly may be wrong with your generator. However, this can still be confusing to those who hope to prevent these problems from happening in the first place. People who have these problems often with their generators usually make a handful of preventable mistakes regarding generator storage or maintenance.

Each generator fault has a root cause, and learning what these are will help you prevent future damage to your generator. We have seen many people become confused as their systems continually need repairs despite preventative repairs being one of the easiest things to do.

Faulty Storage

It’s essential to take the appropriate steps and prepare your generator before storing it. Many generators in all sorts of climates and situations break because they were improperly stored. It’s essential to drain the gas from a generator, clean it, and house it in a dry place for long-term storage.

The better prepared your generator is, the better it will run once you remove them from storage, with the essential thing to do is remove all fuel. Your generator will love you for doing this and allow you to restart the machine with ease even after years of storage.

Low Maintenance

Most likely, the problem with your generator, the low amount of maintenance you have done to it, will naturally cause it to start failing. Before starting the generator each time, you must thoroughly check your machine. Further, you must follow the proper maintenance steps that will protect your generator at all times.

A constant level of maintenance on the simpler parts of the generator will mean that you do not have to spend thousands on maintaining the system properly. Through experience, we have learned that it is always best to maintain the systems constantly rather than only do maintenance once or twice a year.

How Quick Should a Generator Start?

If the generator is maintained correctly, it should only take 10 to 20 seconds to start. A generator starting for the first time will require between 30 seconds and a minute, while older generators can start nearly instantaneously if adequately maintained.

The more worn a generator is, the faster it will start with the more oiled and used parts creating the perfect environment. You will often find that your generator will run perfectly even when conditions aren’t ideal, as most generators are meant to be left alone for most of the year.

When your generator is having trouble starting, it can be as simple as needing more fuel, or it can be a problem that irreparably breaks the generator. If the air filter is crumbling or something worse is wrong, the generator may sustain permanent damage by the failing parts on the inside.

Does a Small Generator Need More Maintenance Than a Larger One?

No, a smaller generator needs no more maintenance than a large generator; the difference is that smaller generators are easier to maintain. As the size of the engine decreases, it will need less oil, and the total amount of filters will decrease as they are no longer required to maintain the system.

Most small, portable generators only have air filters made from a sponge-like material, allowing you to wash the filter instead of replacing them. This is why smaller generators can run for a lot longer without maintenance, as there are fewer parts to break overall.

As the generator you are using becomes larger, it will require more oil, suck up more dust, and generally be dirtier, which means you will have to do the same maintenance on both sizes. Still, a more significant generator will require maintenance much more often as it becomes dirtier.

How Do You Troubleshoot a Generator?

The simple answer is that you should start with the most obvious problems and work your way down to the least obvious problems. Usually, it will be the thing you least expect to go wrong that will be wrong, which is why many people find themselves starting a generator that has no fuel in it.

The only requirement to this rule is that you have been properly maintaining the generator and that you’ve fixed some of the less obvious problems. When starting to troubleshoot a generator, you must keep this in mind, remembering when the last time was you had the machine go through complete maintenance.

Many people strip their entire machines down to the bare bones when only a quick filter change would solve the issue, while others barely run because they need more love.

How Long Does It Take to Fix a Generator?

It should take you no more than two hours to fully repair a generator, while essential maintenance should only be a few minutes to complete. The most extended parts to replace will be the filters and oils of your generator, while just topping up some fluids should be a few minutes at most.

If you need to replace the battery and only the battery on your generator, it will depend heavily on the machine’s manufacturer. Some generators have only a small cover over the battery, while others have the battery hidden somewhere deep and dark.

When repairing a generator, it is essential to remember the last time you serviced the machine; if it is the first time you’ve maintained the generator, it changes everything. It may take many hours or even days to repair a generator if you have not regularly maintained it and kept it in good working order.


There are many reasons your generator may not start, and it can be a problem when it is dark and cold outside. Fortunately, the machines are pretty simple to fix when you have the right tools, and most people around the world quickly learn when and how to do the proper level of maintenance on the systems.

Whatever you do, please don’t try to force the machine to start when it is obviously on its last legs!


Hubert Miles

I've been conducting home inspections since 2002. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and an FHA 203k Consultant. I started PickGenerators.com to help people better understand whole-house and portable generators.

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