Generator Won’t Start? 14 Common Reasons and Quick Fixes

We usually buy generators as an emergency backup. And I can imagine your frustration when during a power outage, you pull your generator out on Christmas, hoping it would save the day, and the generator has starting issues.

A generator sitting around for long won’t start when you need it. 

Here we would discuss the most common reason preventing your generator from the instant start. These can range from obvious ones like the low-fuel to the most overlooked ones like a faulty spark plug. 

Also, keep in mind that you don’t need a professional to troubleshoot the generator. It would be best to stay calm as a non-starting generator doesn’t necessarily mean that it has a damaged component. In most cases, you can apply quick fixes and start the generator within minutes. 

So without further ado, let’s go straight to our first reason, the most common one behind a non-starting generator. 

Generator Tank Is Low On Fuel Or Gas:

One of the basic checks while troubleshooting a generator is to find out if the tank has run out of gas (propane) or fuel (gasoline). If everything is alright, check the valves and tubes for possible closure. 

Also, if you are using old fuel (more than two months age), known as slate gasoline, your generator won’t work correctly. You should remove the old energy and top up the tank with a fresh one. Also, try cleaning the carburetor and fuel valves. More on that later. 

The Engine Is Running Low On Oil:

Apart from the fuel, the engine oil is necessary for the proper functioning of the generator. Low oil may be the cause of your generator starting problems. 

Usually, there is a low-oil sensor preinstalled on the generator that keeps you updated. The sensor stops the generator and won’t allow it to start again if it is low on oil to protect the engine.

 But if you have an old model, use the dipstick to assess the oil level. It is usually located inside a crankcase.

If that is the case, find the right engine oil for your generator in the user manual provided with the product. 

The possible cause of low oil is that you have been running your generator for more than 50 hours (20 hours for new generators) without replacing it, or there is a leak in the tank. 

The Choke Lever Is In The Wrong Position Or Too Opened/Closed:

The choke lever controls the amount of air entering the carburetor. If it is too opened or too closed, the carburetor is not getting enough fuel and air for proper combustion. A surplus can also result in the same problem. 

Most people don’t know the generator’s choke position, which may lead to a frustrating situation. The choke lever is closed at the marked starting point. To open the choke, you align with the marker for a run. 

The choke needs to be completely closed when you’re starting a generator after a long period of rest and opened halfway or fully opened if you start it after a short break as the combustion would occur more quickly. 

Depending on the style and type of the generator, the choke lever can be positioned in different places. It can be found directly above the air filter or is built into the power control knob. 

The Low-oil Sensor Isn’t Working Correctly:

The low oil sensor is a handy feature of the generator as it helps you keep tabs on low fuel. But a malfunctioning sensor is often the root cause of the problem. A faulty sensor would prevent the generator from starting up, even if the oil tank is full.

Sometimes the generator is placed on an uneven surface, triggering the sensor to stop the generator from working. In that case, just put the generator on an even surface as the meter is not broken, but it takes an inaccurate reading. 

If that doesn’t solve the problem, you would have to disconnect the sensor. You would have to pull out the sensor wire you can easily find exiting the engine’s crankcase. Now start the generator; if it works, replace the low-oil sensor. 

Finding the exact sensor is a hard nut to crack, but it is worth it. If you disconnect the low oil sensor from the generator for any reason other than troubleshooting and keep it that way, the generator would run on low fuel without you knowing it, thus cutting its life in half. 

It’s Just Too Cold!

A generator might not be built to withstand harsh weather conditions, especially the low temperature of winters. If you put such a generator to test in extreme cold, you would end up disappointing. 

Most people store their generator in the garage where it catches dust, and bring them out on special occasions: birthday parties, family get together and Christmas. In these cases, the dust clogs up the critical part or simply the chilly outside weather.

If you are in a familiar situation, perform a thorough clean-up and give it a few hours to acclimatize before you attempt to start it. 

Also, you can make a shed for your generator to save it from extreme weather. Installing a heater in the shed would also be helpful.

Modern generators come with a preheat setting that you can attempt before full ignition. There is usually a small light indicator that lets you know whether you can start the generator or not. 

The Flat Battery Of The Electric Generator:

Generators with an electric start are convenient to use. But if not used over time, the battery might lose its charge. It also happens when it is recharged or discharged many times (when using an old model of the generator).

If your generator starts independently via a remote or pushes a button, it is using a battery. 

Check the battery using a multimeter. If the battery is fine, check for a blown fuse and replace it if necessary. It would be best if you also made sure that there is no corrosion on the battery terminals and tight connections. 

If the terminal had been catching dust for a long time, the battery would not work correctly. In that case, you should consider cleaning it with a wire brush (or you can sacrifice your toothbrush). 

A lot of power loss occurs over loose and dirty connections because they resist the electric current. Cleaning and tightening the battery terminals is often all you need to fix a generator that won’t start.

A quick fix is to start the generator using the manual pull starter, also known as the auxiliary recoil starter. Alternatively, if you can charge the depleted battery using a 12 Volt DC charger. You can also buy those cheap AC to DC converters to make use of your home outlets. 

If nothing worked and is provided, there is an emergency, and you can jumpstart the generator using the cable connected to your car battery.

You should seriously consider replacing your battery if it has passed its expiration date (usually three years).

The Carburetor Is Clogged By Old Gasoline Or Airlock.

If the carburetor is not getting enough air due to clogged air filters, your generator won’t start. We have already discussed how to deal with a clogged air filter. 

If you plan to store your generator for a long time (more than two months), it is recommended to drain it completely. Failing to do so would result in inside fuel getting thick and sticky, thus clogging the carburetor. 

A faulty carburetor can affect the overall performance and fuel efficiency of the generator. You may also experience consistent overheat, automatic shutdown, or a dark, black fuel exiting the generator. 

There are many ways you can apply to fix this issue:

Without removing the carburetor:

– Use a fuel stabilizer to prevent slate from getting in the way of fresh fuel combustion

– Try spraying carb cleaner into the orifices and jets. You don’t have to remove the carburetor this way. 

 Old gas can cause clogging in the fuel tank, or it can also reduce the output power of your generator. Make sure that you use fresh gas for your generator. 

Add fresh gasoline when necessary (to avoid clogs and hard starts, do not use old or stale gasoline. If the gasoline is older than two months, replace it with fresh gas)

Removing The Carburetor:

Lastly, you can remove the carburetor for a thorough clean-up. Shut off the fuel valve, and open the carburetor drain found at the bottom of the carburetor bowl. Or You can remove the entire bowl and clean the slate fuel. 

Using a sewing needle or a small brush, clean out the main jet nozzle. As the carburetor parts are susceptible, make sure you don’t damage any of them. Be gentle and patient. Keep track of all the screws; you don’t want to lose any of them.

After complete clean-up, reassemble the parts and open the fuel valve before you attempt to start up again.

If the carburetor is clogged to an irreversible degree, you would have to find a new one. To avoid this in the future, never store your generator for more than one month, and do regular maintenance. 

A Faulty /Glow Plug (Spark Plug Is Having Problems)

Spark/glow plugs are often the culprit behind a generator that refuses to start.

(Note: The diesel generators have glow plugs, whereas gasoline generators have spark plugs to ignite a spark that kicks off a generator. )

You can pull the spark plug manually or use a spark plug wrench included in the toolkit that comes with most generators. Once removed, check the spark plug for possible signs of wear and tear.

Spark plugs accumulate dust and debris over time, or maybe the electrodes are eroded or damaged. If it looks dirty, use a carb cleaner to clean it up. You can also use a small knife to do the job.

However, suppose you notice a large deposit of carbon at the electrodes. In that case, the electrodes themselves appear to have burned away, or the insulating material is damaged; there is no need to wipe it off. 

It would be best if you considered replacing the spark plug. They come very cheaply, and you can buy extra for emergency conditions like these. 

Alternatively, you can use a spark plug tester to check for any fault. If you see a spark, vital with blue color while using the tester, the spark plug is excellent. If not, replacement is all you can do. 

(Note: Do check the ignition coil for possible failure. )

Check The Air Filter For Possible Clogging Or Damage:

If the spark plug is working perfectly fine and still the generator won’t start, the next thing you need to check is the air filter. 

A generator needs an air filter to run correctly. Over time, the filter gets clogged up with dirt, dust, and debris. The carburetor wouldn’t receive enough air, which in turn prevents proper combustion from taking place.

You need to check the generator’s user manual to find out how to open up the air filter. Mostly it is on the side and easily accessible. Pull out the air filter, and check the spongy element inside. Please give it a gentle whack against the floor or the wall to remove the dust, or try shaking off the dust. 

If the dust doesn’t budge and the air filter is damaged beyond repair, you should consider buying a new one for the generator. Fortunately, like spark plugs, they are easy to find and are affordable. You can keep a spare air filter for your generator. 

Check the user manual of the generator to find the right size of the filter. 

Electronics/Cables Are Plugged In During Startup:

Whenever you start a generator, make sure that no cord is plugged into its outlet. Heavy-duty appliances draw enormous power from the generator and should only be run on it when the generator runs smoothly. 

You should ensure that nothing should be plugged into the generator during startup, even the extension cords with no appliances attached on the other end. 

Fuel Degrades Or Water Gets Inside The Tank:

As we discussed earlier, fuel quickly degrades. As we keep the generator away for months, the energies inside it turn into a sticky, thick substance called slate that prevents the generator from starting.

Moisture can also be a cause of your generator starting problem. It can get inside the tank when you are refueling it on a rainy day or by condensation. Opening the tank on a warm, humid day allows the moist air to get inside. Water once inside the generator damages the engine and encourages microbial growth. 

If the fuel gives out an abnormal smell, replace it with the fresh one. But before you do that, thoroughly clean up the tank for possible slate clogging.

Some generators have a fuel filter/water separator sight glass attached that allows you to see if there’s water in the fuel line. Even better, a few models also have a release valve. So if there is water in our diesel tank, you can drain it off.

The Generator Might Have A Coolant Problem:

The coolant is responsible for keeping the temperature of the radiator to optimal levels.

Sometimes the coolant levels are low (due to possible leakage), or the coolant is not flowing correctly. Otherwise, you might have overheated the generator by non-stop usage; the sensor detects this and shuts down the generator.

You can check for the coolant problem yourself, but you would need professional help to fix it if found. Look for hose and belt drive wear, coolant puddles, drips, and crusted areas of dried coolant. 

Sometimes grit, dust, oil, and internal corrosion obstruct the radiator core. Inspect the radiator for cleanliness. Check the coolant for dirt and other contaminants. 

Check for internal coolant leaks by looking for discoloration of the oil. Coolant in the oil will change its color or give it a milky texture. 

If you detect any of these signs, hire a maintenance specialist as soon as possible, as you might end up irreparably damaging your generator. 

Engine Flooding Due To Excess Fuel:

Another primary culprit of generator startup problems is a flooded engine. If excess fuels gather up and go unburned in your combustion chamber, your generator engine is flooded.

A flooded engine dampens the spark plug, making it useless. Without the ignition from the pin, your generator will have starting problems.

If faced with engine flooding, don’t go bonkers at the recoil starter or repeatedly press the electric switch, as these would only make things worse for you. 

All You need to do is to open up the air filter. It would allow the excess fuel to evaporate. Wait for a while, and try to start again. It would possibly fix the generator start problem. 

Fuel Valve Closed or Fuel line blocked.

If the carburetor is working perfectly fine and the fuel tank has enough fuel, the carburetor is not getting enough fuel; the problem is either with the fuel valve or the fuel line. The fuel valve controls the flow of energy from the gas tank to the carburetor.

Make sure the fuel valve is opened before you attempt to start the generator. Also, look for the vacuum relief valve and open it. And after trying all these fails, and the fuel is not flowing from the fuel tank to the carburetor, the fuel line or the filters inside are possibly clogged.

Fuel filters are there to prevent debris from entering the generator. And they often get clogged. You need to detach the fuel line to look for any possible blockage. It would help if you disconnected the outlet hose from the fuel intake side of the valve. (Gasoline may begin to flow as soon as you disconnect, so keep a bucket ready.)

Try to dislodge the blockage if it is possible. Also, look for pinches, twists, cracks, and leaks in the fuel line as they might be the culprit for the generator not starting.

It always helps to keep a spare fuel line with you if you live in a faraway place. 

Final Words:

We have discussed with you the most common reasons behind your generator’s starting problems. 

Let’s repeat them in a list, so you can quickly get the gist of it.

  1. The generator is low on fuel
  2. The engine is running low on oil
  3. Choke lever is in the wrong position or too open/closed
  4. The low oil sensor isn’t working
  5. It’s just too cold outside
  6. The carburetor is clogged by debris
  7. The flat battery of the electric generator
  8. Faulty Spark/Glow plugs
  9. Air Filter Blockage
  10. Electronic cables plugged into the generator
  11. Fuel Degradation and Water contamination
  12. The generator might have a coolant problem
  13. The engine is flooded due to excess fuel
  14. Fuel Valve Closed or Fuel line Clogged


How do you troubleshoot a portable generator?

To cover the basics, follow these steps:

  1. Make sure the generator has enough gas and oil
  2. Use fresh fuel (stale gasoline won’t have enough power to start the generator)
  3. The lever is rightly positioned
  4. The generator is operating in an optimal environment.
  5. The spark plug is working properly

And if your portable generator checks all these boxes, you will have to look for advanced issues like a clogged carburetor and fuel valve.

Six Times An Hour
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