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10 Common Reasons Your Generator Won’t Start

    Generators are such a handy addition to your home. With a generator, you no longer have to worry about blackouts, or how you can power your smoker while on a camping trip. Generators give you access to power no matter where you are, so it is clear why they are such a popular purchase among people. But despite their great functions, just like anything, generators can occasionally develop problems. 

    There is nothing more annoying than switching your generator on, only to find that it won’t start. This might cause a momentary flush of panic, but there’s no need to worry because more often than not, a generator that won’t start is an easy fix. While with a lot of other machinery a non-starter can be a sign of a serious problem, if your generator is not starting, this usually means that something minor has gone wrong. 

    So if you have attempted to start your generator, only to find that it won’t go, then you are in the right place. In this guide, we’re taking a look at all of the common faults that can cause your generator to not start to help you understand what might be wrong with your generator. So let’s get started. 

    What is a Generator?

    Before we take a look at some of the main reasons why your generator may not be starting, let’s quickly make it clear what a generator is. 

    A generator is a device that is able to produce electricity without having to be attached to a mains electricity point. These machines can do this by converting mechanical energy from sources like gas, propane, and diesel, into electrical power which can then be output from the generator. Through this external circuit, the power generated by the device can then be used to provide electricity to other devices. 

    Generators are extremely popular among a lot of people because they give you lots of freedom. They are also popular because they come in lots of shapes and sizes which are all designed to be used in different situations. You can get portable generators that are specifically designed for use on camping holidays or outdoor days out where you want to smoke some food. You can also get much larger generators that are designed to work as a backup electricity supply for your home. 

    The size of the generator doesn’t necessarily dictate the power as you can have portable generators that can output a lot of electricity, just as you can get larger generators that have a much smaller ability. But no matter what you want, the chances are that there is a generator out there that is perfect for you. As well as there being generators available in varying sizes, you can also choose a different generator depending on the type of fuel which you want to power it. So let’s take a look at the different fuel sources you can use for generators. 

    Gas vs Propane vs Diesel

    As we have already mentioned, you can purchase different types of generators depending on the fuel source that you want the power to be generated from. While there are lots of different options available, the main three categories that you can choose between are gasoline, diesel, and propane/LPG. The two traditional types of generators are diesel and gas but in recent years propane generators have become more popular. 

    In the last few decades, there has been a huge focus on the effect that the actions of humans have on the environment that we live in. Both diesel and gasoline are fossil fuels with a known connection to the destruction of the ozone layer. Due to the issues that have been connected with burning these fossil fuels, a lot of eco-friendly consumers tend to avoid diesel and gas machines. So, in line with the increase in popularity of electric vehicles, a lot of people have also started using propane generators. 

    Propane generators are generators that burn propane in order to generate the electricity needed to power external devices. Propane is a popular choice among people who care about the environment as it is a clean-burning fuel, meaning that when it burns, the badness that is let out into the atmosphere is minimal. Propane generators tend to be less efficient than gas or diesel generators meaning that they often require re-fuelling more regularly. However, for many people, they are happy to take the hit in terms of efficiency for the cleanliness associated with propane. 

    Some people who purchase generators in a prepping context also tend to choose propane as this is a type of fuel that will never run out. Propane is man-made and so it can always be generated, whereas both diesel and gasoline will run out of supply at some point. The type of fuel that your generator uses will likely have an impact on the reasons why your generator won’t start. So whether your generator is powered by gasoline, diesel, or propane, let’s take a look at some of the reasons why you might find that it won’t start. 

    A Dead Battery

    One of the most common reasons that your generator won’t start is because the battery has died. To a certain extent, generators operate similarly to cars and so a dead battery is an obvious reason why your generator won’t ignite. However, that being said, a dead battery will only be able to affect certain types of generators. 

    Only generators that come with an electric start will be able to be affected by a dead battery. But the majority of generators now come with an electric start whether it be from a button on the generator or a separate remote which can be used to turn on the device. For the electric starter to be able to work it has to have an active power source that comes from the battery. So if you know that your generator has an electric starter, there is a good chance that the reason it will not start is because of the battery. 

    To test if it is really the battery that is causing the problem you can attempt starting it with the auxiliary recoil starter. Not all generators come with these starters, but if yours has one it is an easy way to test if the battery is dead. If the generator will start using the recoil starter, then you know the problem lies in your battery. You can then charge the battery using the DC outlet on your generator. Similarly, if your generator does not have a recoil starter, we still recommend charging your battery in case this is the reason why your generator won’t start. 

    Alternatively, you can jump-start the battery of your generator in the same way that you would jumpstart a vehicle. However, if you have time to charge your battery we would recommend doing this instead of using jump leads to get it running again. 

    If charging the battery doesn’t work, then the problem must lie elsewhere. Let’s take a look at another reason why your generator won’t start. 

    Low on Oil

    If you have recharged the battery of your generator and it still won’t start, or your generator does not have an electric start, then the problem must be somewhere else in your generator. Following a dead battery, another common reason why your generator may not start is because it is low on oil. 

    While fuel is incredibly important for your generator to be able to run smoothly, another component that is often forgotten but just as important is oil. Without oil, your generator will be unable to operate, so if your generator won’t start, there is a fair chance that it is low oil that is at fault. However, before we go any further we must note that most modern generators will come with precautions in place to prevent the generator from running out of oil, including things such as low oil sensors or low oil shut-down mode. 

    But if your generator does not include these precautionary measures, then it might not start because the oil has run low. Most generators will come with a set amount of hours that they can run before the oil requires refilling, however, it is easy to forget when you refilled it last. Low oil could also be caused by a possible leak which is more likely if your generator is an older model. 

    To test if the reason that your generator will not start is low oil, you can easily check the oil level using the dipstick. The dipstick is usually located within the crankcase of your generator and can be used to check the oil level of your generator in the same way you would check the oil level of your car. Different generators will come with ideal oil levels, so you should check the handbook for your generator to see whether this is the reason that your generator will not start. 

    If charging the battery and refilling the oil is unsuccessful, there’s no need to worry because there are plenty of other reasons why your generator may not start. 

    Low on Fuel

    Another incredibly common reason that your generator won’t start is because it is either out or incredibly low on fuel. As we have already discussed, generators are able to produce power through the burning of fuel, so if the fuel is running low this could cause the issues you are experiencing with your generator. 

    You might read this and be thinking… Duh. But often in a time of crisis, it is the most obvious answers which are overlooked, and so it is definitely worth checking the fuel levels of your generator. If you check the fuel tank of your generator only to find that it is empty, then we are almost 100% certain that this is the reason why your generator will not start. It is easy to check the fuel tank of a gasoline or diesel generator as you will be able to see whether there is any fuel left in the tank, but it is slightly more difficult with a propane generator. 

    Propane generators operate by being directly connected to a tank that contains propane. They are connected through a series of tubes that connect the fuel openings of the generator to the valves on the propane tank. To check that there is a constant supply of propane from the tank you need to check that all the tubing and valves on the propane tank are open. 

    Another reason why your generator may not start that could be connected to the fuel is if the gasoline in the tank has gone stale. You should never hold gasoline over the age of 2 months in the fuel tank of your generator as this can be extremely damaging, so you must regularly clean out and replace the fuel in your fuel tank. 

    If you check your fuel tank only to find that the generator has a decent supply of fuel left, then this is not the issue why your generator is not starting, so what else could it be?

    The Choke is Too Open or Too Closed

    If the battery, oil, and fuel of your generator are all operating well with a steady supply, then this is not the cause of why your generator will not start. The next thing that we recommend checking is the choke as this could be the cause of the problem. 

    It is the choke of the generator which controls the amount of air that enters the carburetor during the start-up function of the device. You will usually be able to check if the choke is at fault by what happens when you attempt to start the generator. A generator that is being affected by too little or too much air will attempt to start up but ultimately fail to turn over, meaning that it is very different from the sounds made by a generator with a dead battery. 

    It is common for generators that are cold to experience issues with the choke. When the generator has not been started for a while, you should set the choke to closed which is often labeled as ‘start’ on the generator’s controls. Once your generator is running, you can then begin to open the valve for the choke. Likewise, a generator that is not being started from cold might require the choke to be partially open during startup. 

    If you are attempting to start your generator, only to find that it will not go, it could be because the choke on your generator is set to the wrong setting. You may have forgotten to close the choke after using your generator last, and this could be the reason that it is not starting. Likewise, you might be restarting your generator while it is still warm which means that the choke has to be adjusted to fit the temperature of the generator at the starting point.

    If you find that there is no issue with the position of your choke, then the reason why your generator is not starting must be something else. 

    A Clogged Carburetor 

    Another issue that could be causing your generator not to start is closely linked to the choke, and that is the carburetor. The carburetor is the component of the generator that mixes the air and fuel together for internal combustion to occur, allowing the generator to produce electricity that can then be output into other devices to provide them with power. 

    The carburetor performs an essential function within the generator, and without the carburetor, your generator will be unable to operate properly. Issues with the carburetor do not commonly occur when the generator is being used regularly, instead, this tends to be something that develops during the time that your generator is in storage. As it affects generators that have been placed in storage, issues with the carburetor commonly tend to affect portable generators which get used more often in certain months than others. 

    When the generator is not being used, it is common for old gasoline to clog together and block the carburetor from being able to function properly. This blockage means that new gasoline is unable to enter the carburetor which prevents the internal combustion process from occurring. Thankfully, this is an issue which you will easily be able to identify by simply looking at your carburetor. 

    If your carburetor appears dirty, then you should wash it. If you cannot see any blockages but feel that this may be the cause, it is also a good idea to give your carburetor a wash. This is very easy to do. All you need to do is close the fuel valve and remove the bowl which lays at the bottom of the carburetor. Using a combination of towels, brushes, and a needle or safety pin, you can easily clean out any fuel debris and poke out any potential blockages. Once you have cleaned the carburetor, you can then reattach it to the generator. Switch the fuel valve back on and see if your generator will start. 

    If it starts, then the issue must have been a blockage in the carburetor. If it does not, then the issue must be somewhere else in your generator.

    A Clogged Fuel Line or Valve

    While a clogged carburetor could be the reason why your generator will not start, there are some other components that can become blocked that will prevent your generator from starting. One of these components is the fuel line, and another is the fuel valve. 

    Similarly to a clogged carburetor, both the fuel line and fuel valve tend to become clogged if the generator has been stored away with fuel either in the tank or in the carburetor. The fuel line and valve tend to become clogged after the carburetor, so if you have cleaned your carburetor but your generator still will not start then this could be the reason why. After you have cleaned the carburetor, you should then move onto the fuel line and valves. 

    Before you do anything else, you first need to ensure that the fuel valve is open and that the vacuum relief valve of the generator is also open. Not all generators come with a vacuum relief tank so you only need to open this if your generator has one. Following this, you should attempt to start your generator as this might have done the job. However, don’t be alarmed if it has not. 

    If that attempt is unsuccessful, you should proceed to unplug the hose. You need to do this by disconnecting the hose from the inlet side of the fuel valve as this will allow you to see if gasoline is able to travel through the hose. This can be a messy task, so you should always have a bucket and some towels at the ready to catch any fuel that may spill out. As well as doing this, you can also disconnect the fuel line to look down it to check for any visible blockages which could be preventing it from working. However, simply disconnecting the one side often proves successful in getting the generator running again.

    If none of the causes that we have looked at so far appear to be at fault, there is a fair chance that the issue could be mechanical, so let’s have a look at some common mechanical issues that affect generators. 

    A Problem with the Spark Plug

    The first mechanical problem which could be affecting the operation of your generator is the spark plug. This is another issue that not only affects generators but also affects vehicles and it is not uncommon for spark plugs to play up or fail to operate properly. 

    Thankfully, an issue with the spark plug is usually easy to identify through the interaction that the generator creates when you attempt to start it. If there is an issue with the carburetor or fuel line, the generator will produce some noise as it struggles but fails to start. If there is an issue with your spark plug then the engine of the generator will do absolutely nothing when you attempt to start it. 

    While identifying that the spark plug could be the cause of the issue is simple, getting a diagnosis is not and this is quite a fiddly job to complete. The first thing that you need to do is locate the spark plugs on your generator’s engine and remove them using a spark plug socket. That might seem simple, but it is once the spark plug is in your hands that the job becomes fiddly. 

    You should check the appearance of the spark plug, looking for any dirt or deposits which could be affecting how it operates. It is normal for deposits to develop upon the surface of your spark plugs, and these deposits can usually be removed easily with a light brush. However, if the deposits do not easily brush away, or you observe broken electrodes or porcelain, then your spark plugs are probably beyond repair. 

    If your spark plugs appear beyond repair then you will need to buy new spark plugs to replace the broken ones. If your spark plugs look like they just needed a clean, then once you have brushed them, you can place them back into the area that you got them from. You should then attempt to start your generator again. 

    If you thought your spark plugs simply needed a clean but this does not work, then you might need to replace them. However, if you replace them and your generator still won’t start then the issue has to be something else. 

    A Malfunction with the Low Oil Sensor

    Another issue that could cause your generator to fail to start ironically lies in a fail-safe which is supposed to allow your generator to work safely, and that is the low oil sensor. The whole point of the low oil sensor is that it shuts down your generator if there is not enough oil in the engine to prevent damage. However, when the low oil sensor stops working properly, it can stop your generator from starting up, no matter how much oil you have in it. 

    The reason behind the malfunction could simply be because your generator is not on a flat and even surface. Uneven surfaces can cause the sensor to misread oil levels and incorrectly prevent the generator from starting. However, this is not the only reason why your generator may not be starting and so to check if there is an issue with the low oil sensor, you need to disconnect it. 

    As the sensor is not an essential part of the generator, the generator will start without the sensor connected. So once you have disconnected the sensor, you should attempt to start the generator. If the generator starts like normal then the sensor must be the reason why it would not start earlier. Thankfully, fixing this issue is normally very simple, and all you need to do is leave the generator run for a few minutes before you reconnect the sensor. However, if the generator immediately shuts down when you reconnect the sensor then you will have to buy a replacement.  

    It is always worth double-checking that you have plenty of oil in the generator to ensure that it is a problem with the sensor and that the reason isn’t because you have a low level of oil in the engine. Replacing the oil sensor is a tricky task and the last thing you want to do is go through this hassle only to find that the real cause was low oil. 

    Unfortunately, if this still does not fix the issue, then it has to be somewhere else in your generator. 

    Your Air Filter Needs Replacing

    This next reason that your generator will not start is closely linked to the choke. If you found that adjusting the choke by either making it tighter or looser helped your generator but unfortunately could not solve the problem, then you should perhaps take a look at the air filter. 

    The choke is directly linked to the air filter which is why adjusting it might have appeared to help to a certain extent. However, no matter how much you open or close the choke it will not make a difference if your air filter is clogged. A clogged air filter will prevent air from traveling into the carburetor which in turn will prevent the carburetor from being able to do its job. The carburetor requires a certain amount of air to be able to work and if it cannot get this amount of air it simply will not work. 

    Thankfully, this is a fairly easy issue to identify and solve as the air filter is easily accessible. So once you have located your air filter, you simply need to detach it and take a look at it. If the air filter appears dirty, dusty or clogged then it will require replacing. Once you have replaced the air filter, you should move the choke back to the start position and attempt starting the generator. 

    If it starts then the air filter was clearly at fault. However, if you can still not get the generator to start then the issue could be something else. With that in mind, let’s take a look at the final thing which could be preventing your generator from starting. 

    Cables are connected to the Generator

    A final thing that could prevent your generator from starting properly is the cables that are connected to the generator. This might seem a bit too obvious, however, it is surprising the number of people who cannot get their generator to start, only to find it is because they have devices connected to it. 

    When you purchase a generator, it is made absolutely clear that the generator should not be started when there are cables connected to it. This not only includes direct connections to appliances but also connections to extension leads that are not directing the electricity anywhere. 

    Compared to the other reasons that we have looked at, this reason might seem too good to be true. However, if you attempt to start your generator and find that it is not working. The first thing you should do is check if it is connected to anything. If it is, then the chances are it is these connections that are preventing the generator from starting. Simply detach the cables from your generator and then attempt to start it again. If it starts then the issue must have been the connections, if it does not then we would recommend checking out the other reasons that we have looked at above. 


    In short, there are lots of reasons why your generator may not immediately start. Some of these reasons can be as simple as your generator being connected to an electrical appliance, however, in other cases, the reason can be a lot more serious. Thankfully, the majority of issues connected with a generator that will not start are easy to diagnose and also easy to solve. So if you have tried to start your generator, only to find that it will not bite, check out this guide for some of the top reasons why your generator may not start.