What To Do If Your Generator Won’t Start?

Last Updated on March 4, 2025

We can become pretty dependent on our generators, especially in the cold months, or for those of us who live in areas prone to hurricanes or tornado alley. Whatever the reason or location, is important to have a dependable generator on standby.

If your generator won’t start, it’s a frustrating experience, especially since it is probably due to a minor issue that you have to now track down, such as fuel filters, spark plugs, carburetors, air filters, or just low fuel in general.

Generators are usually for seasonal usage—or, at least a season or timeframe of the year which is convenient and works for you—so its always a good idea to break it out a month beforehand, crank it up, let it run, and do your own diagnostic by looking it over as it runs. 

It’s all part of preventative maintenance, the one thing that will keep your generator running longer than any other. Keeping it in good shape beforehand ensures that it will be in good working condition when you haul it out and clear off the dust. 

Reasons Your Generator Won’t Start

If the generator was running just fine the last time you used it and, since for most people, generator usage is seasonal and a machine of convenience, one of the first problems that you may not be aware of is shelf life.

Reason	What To Do
Gasoline Expires	Use a stabilizer such as Sta-bil Fuel Storage Stabilizer
Carburetor	Purchase something like Sta-bil Fast Fix and get yourself a wire brush
Fuel Lines/Fuel Valve/Fuel Filter	Make sure that your fuel line is open, check for blockages in the line or filter.
Spark Plugs	Put a multimeter on it and test it when it is operating
Ignition Coil	Replace the spark plug
Air Filter	Clear your air filter of debris.

Gasoline Expires

Well, it doesn’t really expire but it does have a shelf life, and sitting for long periods of time will certainly dilute its efficacy.

There are two ways to deal with gas that is no longer up to the task: put in fuel additives the next time your generator goes into storage, empty the tank and refill it with good gasoline. 

What we mean by “additives” is using a stabilizer, such as Sta-bil Fuel Storage Stabilizer. This will ensure that the first time you crank up your generator, you don’t do any damage to the internal parts with stale gasoline, which would make your day even worse.

Sta-bil and others like it, keep your gas from going stale in storage. Most of the ones on the market today are designed for gas and ethanol mixtures since that’s the most common gasoline we get at the pump.

However, it will also work just fine for regular, unleaded gasoline.

Carburetor

The carburetor is going to have problems whenever bad fuel flows through it. Even so, it may accumulate carbon build-ups and additional gunk over time. If you think that there is a fuel problem, the carburetor is an easy one to clean and check.

If your generator isn’t starting, putting a fuel additive in to clean the carburetor is a loss/loss scenario. You have to get it running for the fuel additives to do the work. So the best thing that you can do is remove it completely and clean it. 

Purchase something like Sta-bil Fast Fix and get yourself a wire brush. Remove the carburetor, dip the brush in the carburetor cleaner and go to work. If it is really clogged, you can try blowing it out with an air compressor. 

Either way, don’t put it back in until the thing looks like you just pulled it out of the box after purchasing it.

Once you’ve replaced it and you get the engine running again, then go ahead with your additive, which includes pouring the rest of the Sta-bil Fast Fix into the fuel.

Fuel Lines/Fuel Valve/Fuel Filter

A combustion engine needs three things in order to create the chemical and explosive reaction required to convert into power: Fuel, oxygen, and spark.

Whenever you’re having trouble cranking up a generator, remember those three things and start working your way through them.

Now that we’ve dealt with one aspect of fuel, it’s time to eliminate the rest. Fuel lines are a common issue, especially in generators that spend a lot of time on the shelf, waiting for a particular season to roll around. 

The fuel valve is important for two reasons: one, if it’s not open, you’re not getting the fuel you need to crank up the generator, and two, you can use it to remove and inspect the fuel line and filter for clogs or blockages. 

Always make sure that your fuel line is open before you try cranking it up for the first time. If that doesn’t seem to be the problem, shut off your fuel valve so you can check the lines and filter for blockages.

You can turn the fuel valve on and off when you have one end of the line off to see if fuel is flowing freely or not. This will let you know if there is a clog in the line or in the filter. Fuel filters don’t always come on generators so check online or in the user manual to see if yours has one.

See Also: Top 7 Quiet Generators In 2022 [Expert Review & Buying Guide]

Spark Plugs

Spark plugs are one of the most common factors when it comes to small engine problems, whether that’s a lawnmower, weed eater, or generator. Fortunately, spark plugs will throw up a lot of red flags if they are failing. 

• Rough engine idling
• Difficult to crank
• Weak or reduced performance issues
• Sputters and misfires more and more frequently
• Engine light (if your generator has one)

The positive side of all of this is that it is pretty easy to check your way through your spark plugs.

A common misconception is that spark plugs only ignite to get the combustion process started, then they just sit back and enjoy the show until the next start.

However, that’s not true as spark plugs will continue emitting a spark as the engine runs and for as long as the engine is running, which makes them an invaluable part of the system.

To check them, you’ll need to remove each one. 

• Remove a single spark plug
• Check it over for any grime build-up
• Check it for carbon build-ups
• Check it for any signs of cracks
• Use a multimeter and test the spark plug when the engine is cranking
• Ohms should be between 10,000 and 15,000

The easiest way to check a spark plug is to put a multimeter on it and test it when it is operating, which is to say, while the engine is trying to crank. If you have a pull-start generator, you’ll need someone to throw their shoulder out for you so you can test the spark plugs as they crank away.

Ignition Coil

The ignition coil is situated behind the spark plug in the great, big scheme of things, and it’s always important to work your way back in any system that has failed. Ignition coils are responsible for sending the current up through the spark plug.

You’ll know that you have a potential ignition coil problem if you slap a brand new spark plug on there and that new, shiny sparkplug is every bit as useful as a paperweight. 

To test the ignition coil, you simply need to remove the spark plug in order to get to it. Don’t worry, these things are highly effective and insanely cheap. You can get one at your local auto store or on Amazon for about $7 or $8 bucks.

If you’re savvy enough, you can make one yourself. All it does is fit into the socket where the spark plug was and if there’s power there, you will see a light and if there’s no power, you’ll see nothing.

Clean Air Filter

Oxygen is the next suspect and to be fair, it’s usually not the problem. However, if you’ve eliminated the above and you have yet to find the issue, checking the air filter is a good start. The only real thing that can mess up an air filter and give you problems starting, is dirt and debris.

You have to have a clean air filter so that air can move quickly and cleanly through it, feeding the combustion process with what it needs.

The argument can even be made that air is more important to the combustion process than fuel. After all, oxygen is far more explosive than gas at high levels. 

Simply pull out your air filter and check it over. Make sure it’s completely clear of all debris and that the filter itself is in good working order, not yellowing too much and the material is not too degraded. 

See Also: What Will A 3500 Watt Generator Run?

Preventative Maintenance

Preventative maintenance is just as important as any kind of maintenance you do while trying to get your generator up and running again. In fact, proper preventative maintenance may help you avoid having to sit down and work your way through the fuel, air, and spark routine.

Always check your oil filters and oil levels in addition to checking over your spark plugs from time to time, your air filter, and keeping quality gasoline in there that isn’t stale.

If you don’t put a fuel stabilizer in there over the long periods that it’s not operating, empty the old out before you start with something new.

Practicing proper preventative maintenance on your generator is just as important during the offseason as it is when it’s in heavy use. Keep it clean, run it from time to time, and periodically check the most important systems and you will avoid a no-start in the future. 

Related: How Long Can You Run A Generator Continuously?

FAQs

How Do You Unclog a Carburetor on a Generator?

For minor clogs, an additive will likely be enough to unclog it. Run some Seafoam Motor Treatment through it and run the generator for a while. If it doesn’t unclog it, you’ll have to move on to more labor-intensive methods. 

For serious clogs, the carburetor will not only have to be removed but completely disassembled. You won’t need any sort of special additive, just warm water, a soft wire brush, and a mild detergent. Scrub each part and thoroughly dry before reassembling.

Why Did My Generator Suddenly Stop Working?

There are a lot of reasons this can happen. With gasoline generators, it seems like it a lot more of a common occurrence than others, but the problem is usually pretty simple.

• It’s out of gas
• Low on oil
• Choke is in full position
• The air filter isn’t allowing enough air through
• The fuel shutoff valve is closed
• Overloading (too many devices plugged in)
• One or more spark plugs are bad

How Do I Manually Start My Generator?

Most generators have the pull-cord feature along with a key start or a push-button start mechanism. If yours has a key or a push-button, then the pull-cord is a secondary option when the other doesn’t work.

Make sure that your fuel valve is open and the choke is on (usually to the right). Press the button or turn the key to crank up the generator. If it fails to crank, go to the pull-cord method instead. Once the motor is running, pull the choke tab back.

Generator Won’t Start After Sitting

When this happens, it’s almost always because the gasoline in the tank is no longer any good. During the off-season, if you choose to leave fuel in the tank (which you should probably empty out or run it through), you should use a fuel stabilizer.

Without one, the gas may no longer be any good. You will have to empty out the tank and refill it with fresh gas. Give it a few turns to work its way into the carburetor but it should start back up.

If it still won’t start, you’ll have to go through the list from above, checking each component to ensure that everything is in good working order.

Generator Won’t Start After an Oil Change

Generators are designed with several fail-safe switches, one of which has to do with the oil. If you have too much or too little, the generator won’t start because that fail-safe switch has been triggered.

Also, using the wrong type of oil may trigger the switch because the generator thinks you have too much or too little. Be sure to check your oil levels and make sure that you are adding the right oil type.

You may also have a faulty oil switch. You can bypass it by locating the switch on or around the oil pan, tracing down the wires, and disconnecting them. It will allow you to crank up the generator when needed until you can replace the oil switch.

Generator Won’t Start After Running Out of Gas

This can happen because the tank was so empty that when you poured in the new gas, the fuel isn’t getting through to the carburetor because of air pockets. First, make sure that your fuel valve is all the way open.

Also, if your generator comes with a primer (a soft, rubber button that you can depress) prime it three, solid times. If it doesn’t have a primer on it, you’ll have to do things the old-fashioned way.

With the fuel valve open, rock, tilt, or shake the generator back and forth. The idea is to get the new fuel running through the system. Be careful not to go too hard on it, however, as you don’t want to flood it when you’re just trying to get enough gas in there to start the combustion process.

How Do I Know if My Generator is Flooded?

Unless your generator is see-through, you won’t necessarily know that it’s flooded so much as make an educated guess. Engine flooding is a common occurrence in generators so it’s certainly not something to be alarmed over.

It basically means that you have so much fuel in the combustion chamber that it’s reached the spark plugs and they are wet with gasoline. There are several ways to deal with it.

• Let it sit for 10 to 15 minutes, giving the gas some time to evaporate
• Remove the spark plugs and dry them off
• Crank it a few times to get some air movement over the spark plug
• Spray starter fluid directly into the air filter chamber (after removing the air filter)

If you try the last one, you’ll have to be quick. Replace the air filter and crank it as fast as you can.