What to do if your Briggs and Stratton generator won't start.

Generators are essential for many homes and businesses but occasionally they won’t start if left sitting in your garage for a few months. In this post, we will be going over why the popular Briggs and Stratton generator won’t start. But more importantly, the tips and tricks to start generators with one pull every time.

We will mostly cover Briggs and Stratton generators but the tips mentioned here will apply to all petrol and diesel generators. What to check and how to maintain your generator so it will last for many years.

Why Generators don’t start easily?

Why Generators don't start easily?
My Briggs and Stratton generator sitting on a shelf for many months of the year.

Most petrol (gas) generators are designed with an internal combustion engine that turns an AC coil winding to generate electricity.

Speed controllers, governors, and voltage regulators maintain a constant electrical output up to the power capacity of the generator. This combustion engine is usually 4-stroke but there are a few older 2-stroke generators still out there in the market.

If the generator is used weekly then starting issues are usually nonexistent due to regular use. But in my experience as an electrician, most contractors, homeowners, or campers only use them a few times a year.

After a few months, the fuel gets old and can gum up inside the carburetor. Moisture can get into the electronics and start to corrode some of the wirings. Starting your generator every month for 5 minutes can help keep the generator in peak condition.

10 reasons that could cause a generator not to start?

10 reasons that could cause a generator not to start?
One of my generators was having trouble starting.

Old fuel.

Generators tend to only have small fuel tanks and they need to be topped up often. This cuts down on weight and makes them easy to work on.

If the generator is left for a few months the fuel gets old and will lose its combustion power. Stale or old fuel will cause a generator to not start easily. Products like fuel stabilizers can help prolong the life of the generator fuel but I like to drain the fuel tank and start fresh if I know I won’t be using the generator for 2 months or more.

Old gummed-up fuel in a carburetor will need to be drained if you are having trouble starting the genset. Having old fuel is the no1 reason my Briggs and Stratton generator won’t start.

Dirty spark plugs

4-stroke generators tend to not foul spark plugs as much as the 2-stroke generators. I still tend to replace my Briggs and Stratton q6500 spark plug every year or 100 hours whichever comes first.

Check the Q6500 spark plug gap this should be 0.76 mm for the Briggs and Stratton 798615 Spark Plug.

This gives me peace of mind that the spark plug is good and will be reliable when I need to start the generator.

Clogged air filter

Briggs and stratton generator clean air filter

Generator air filters tend to be overlooked and missed in preventative maintenance. I like to replace my air filter every year or 100 hours, whichever comes first. This makes sure that the generator can breathe properly. If you have an air filter that looks like a sponge you can wash these out with warm soapy water. Coat them with a layer of air filter oil for excellent dirt trapping properties.

Good airflow is essential for a combustion engine to easily start. remember air filters will break down over time so replace them regularly. A blocked air filter is another reason the Briggs and Stratton generator won’t start.

Low engine oil level

Briggs and stratton generator oil fill

Most modern portable generators will have a low oil cut-off switch. I have seen generators cut out and hard to start with the engine oil at just over the 1/4 mark. Ensure the engine oil is close to the 100% full mark.

I like to replace my generator engine oil once a year. Even if I only use the generator a few times it is best to do once-a-year preventative maintenance.

Briggs and stratton generator oil drain

If your generator does not have an engine oil drain plug you can use a manual vacuum dipstick oil change pump to remove the old oil.

The low oil indicator on the Q6500 Briggs and Stratton generator is designed to prevent engine damage caused by not enough engine oil. If the engine oil level drops below a preset level, the red LED low oil indicator light comes on and an oil level switch will stop the engine. If the engine stops or the red LED low oil indicator light comes on when you pull the recoil handle, check the engine oil level.

The oil level should be checked prior to each use or at least every 8 hours of operation.

Clogged fuel filter

Clogged fuel filter on a generator trouble starting

Most generators will have a fuel filter either inside the fuel tank or in the line going to the carburetor. These are generally reliable but over time can block up. You can back flush them for a quick fix but I tend to replace them every 5 years.

Trace the fuel lines to see where the fuel filter is located on your generator. The quick-release clamps make changing the fuel filter fast and easy.

Faulty Carburetor.

Briggs and stratton generator Faulty Carburetor

A carburetor is made up of 5 main parts that can be prone to failure.

  • Main jet
  • Float
  • Choke
  • Valve
  • Throttle

In my experience, it is dirt that often blocks up parts of the carburetor. When this happens the generator will be hard to start and the carburetor will need to be overhauled or replaced. Here is a list of all Briggs and Stratton carburetors.

Dirt can come from either the fuel or the air filter. Make sure to find out where the blockage is coming from otherwise you will have the same faulty carburetor in the future. Often it is an air leak, faulty air filter, or damaged fuel filter.

Be sure to clean or replace the fuel filter if you find any dirt in your fuel. Old metal fuel cans tend to deposit rust and paint chips into the fuel. Plastic fuel cans are the best.

Electrical fault

Earth fault, stop button, short circuit, overload, and wet electronics are all reasons that could cause your generator to not start.

I spent 1/2 hour trying to start a generator one day just to find out that someone had pressed the emergency stop button. Be sure to check all the basics first. Spark plug lead, e-stop button, run position, choke, oil level switch, and fuel.

Faulty Choke

A choke is used for easy starting on electrical generators. Just like on lawnmowers a choke is used to allow extra fuel/air into the engine where it is mixed at a high ratio for a quick start.

The choke must be closed for the correct operation of the generator motor. Check the choke cable to see if the choke is being operated smoothly and if the cable has not come off the choke arm.

The choke will pull more fuel into the piston area for easy starting. Using starter fluid is another option to help get the generator started, but you must have the choke valve open to spray it in. If you don’t have any quick start fluid you can try these starting fluid alternatives.

Air leakage in fuel lines or exhaust system

Any air leakage in a sealed petrol motor will make it hard to start. Often a hole in the fuel system will make it easy to detect. On the other hand, a blown gasket on the exhaust or the intake manifold carburetor will be hard to fault find.

A can of smoke is handy to see where any air leakages are occurring. Just squirt it sear a suspected leak to see if it is being drawn into the leakage or being blown away.

Low compression

If your electrical generator has low compression it will make it hard to start and will blow a lot of smoke.

Low compression in the piston-cylinder can be caused by a number of reasons such as a loose spark plug, wear on the piston or rings, exhaust or intake valves not sealing, or wear on the cylinder bore walls.

A loose spark plug is an easy fix whereas any wear on the piston, rings, or the bore will require an engine rebuild.

How to start a Briggs and Stratton generator

What to do if your Briggs and Stratton generator won't start.

NOTICE Always have QPT (Quiet Power Technology) switch OFF (0) when starting or stopping the generator or when using DC USB ports.

Disconnect all electrical loads from the generator. Use the following start instructions:

1. Make sure the generator is outdoors on a level surface.

NOTICE Failure to operate the unit on a level surface may cause the unit to shut down.

2. Pull choke control out to close choke (NOTICE For a warm engine, be sure the choke lever is in RUN) position.

3. Turn the engine switch to the ON green position.

4. Grasp the pull-start recoil handle and pull slowly until slight resistance is felt. Then pull rapidly to start the engine.

5. Open the choke butterfly valve gradually as the engine warms up by pushing in on the choke handle.

Briggs and Stratton 2200 generator won’t start troubleshooting tips

Briggs and Stratton 2200 generator won't start troubleshooting tips

Remember, a small generator motor only needs 4 things to start up. Air, fuel, spark, and compression.

Replace the fuel first with brand new gas.

Clean the air filter and leave the air filter out at this stage.

Remove the spark plug and replace it if necessary. You can check the spark by connecting the removed spark plug to the lead and placing it on the metal engine block. Pull the starter cord and look for a spark. If you have a spark, check the spark plug gap and adjust if necessary. Sscrew in the spark plug and torque down.

Squirt some starter fluid into the air filter intake port with the choke valve open. Replace the air filter and screw on the cover.

You should no be able to start the Briggs and Stratton 2200 generator.

How do you start a generator that has been sitting for a while?

If your generator has been sitting for a while and not used then do the following before trying to start it.

  • Check/replace the spark plug
  • Check/replace engine oil
  • Drain the fuel out of the tank and carburetor. Replace with new fuel.
  • Inspect the air filter for contamination such as dirt and insects.
  • Turn off all electrical loads connected to the generator.
  • Reset any overloads or e-stop buttons.
  • Turn the generator to the run position.
  • Squirt some engine starter fluid spray into the air filter intake.
  • Pull on the starter cord to start up the generator. The easy start spray will often give you a perfect one pull start.

How long can gas sit in the generator?

In general, 91-98 octane pure gas begins to degrade and lose its combustibility as soon as it is exposed to the atmosphere. In a sealed container, you can expect to get between 4-6 months of shelf life. If it is stored in a generator the gas shelf life will be less due to the fuel cap having a vapor release valve. As a result of oxidation and evaporation expect to get between two to four months of shelf life of fuel used in a generator.

Should I drain the gas out of my generator?

If you haven’t used the generator in over 5 months I would drain the fuel out of the generator and dispose of it. New clean fuel will make your generator easy to start and run reliably without any hunting or speeding up/slowing down of the genset.

Fuel can become stale when stored over 30 days. Stale fuel causes acid and gum deposits to form in the fuel system or on essential carburetor parts. There is no need to drain gasoline from the engine if a fuel stabilizer is added according to instructions. Run the engine outdoors for 2 minutes to circulate the stabilizer throughout the fuel system before storage.

If gasoline in the engine has not been treated with a fuel stabilizer, it must be drained into an approved container for long-term storage.

Check out this quick video on how to use easy quick start spray to start a generator.

Briggs and Stratton Q6500 problems and solutions

Briggs and Stratton Q6500 problems and solutions
The engine is running, but no
AC output is available
1. Red LED light is steady. Generator is
overloaded or overheated.
2. Poor connection or defective cord set.
3. Connected device is bad.
1. Remove loads from the generator.
Press the OVERLOAD RESET button
on the control panel.
2. Check and repair.
3. Connect another device that is in
good condition
The engine runs well at no-load
but “bogs down” when
loads are connected.
1. Generator is overloaded.1. Remove loads from the generator
The engine will not start;
starts and runs rough or
shuts down when running
1. Engine switch set to OFF (0) position.
2. Low oil indicator light comes on. Low
oil level.
3. Out of fuel.
4. Spark plug wire not connected to
spark plug.
5. Flooded with fuel
1. Set the switch to the ON (I) position.
2. Fill the crankcase to the proper level or
place the generator on a level surface.
3. Fill the fuel tank.
4. Connect the wire to the spark plug.
5. Wait 5 minutes and re-crank the engine.

For the maintenance schedule please follow hourly or calendar intervals, whichever occurs first. More frequent service is required when operating in dusty adverse conditions.

First 5 Hours Change the engine oil

Every 8 Hours or Daily

• Clean debris

• Check engine oil level

Every 25 Hours or Yearly Clean engine air filter

Every 50 Hours or Yearly Inspect the muffler and spark arrester

Every 100 Hours or Yearly

•Replace engine air filter

• Replace the spark plug and change the engine oil

Briggs and Stratton q6500 oil type

  • SAE 5W-30 Synthetic Engine Oil
  • Formulated for air-cooled, 4-cycle engines in outdoor power equipment
  • For use in all air-cooled 4-cycle engines such as generators and lawnmowers.
  • Warranty approved for Briggs & Stratton engines

Briggs and Stratton q6500 spark plug

Briggs and Stratton 798615 Spark Plug. Replace every 100 Hours or yearly.

Briggs & Stratton genuine parts are specially designed to exact Original Equipment Manufacturer (OEM) standards. Not only are Briggs & Stratton genuine parts assured to fit, but using them ensures that the Briggs & Stratton engine they are installed on complies with applicable (EPA) emission regulations and helps maintain valuable warranty coverage.

Briggs and Stratton q6500 fuel consumption

The Q6500 QuietPower™ Series Inverter Generator can run for 14h at 1/4 load. The higher the electrical load the more fuel will be required to power the genset. Using QPT (Quiet Power Technology) will also affect fuel consumption. The fuel tank capacity on the Briggs and Stratton Q6500 is 18.9 Liters.

Briggs and Stratton wiring diagram

Briggs and Stratton wiring diagram

Briggs and Stratton Q6500 manual

The Briggs and Stratton Q6500 manual can be downloaded here.


The Briggs and Stratton Q6500 is an amazing piece of technology. The only reason I find that it doesn’t start is that it has old fuel in it. I really like my genset due to how quiet and reliable it is.

As long as you do some preventative maintenance every year you should have trouble-free running on your generator. Remember if storing your generator away for a few months always drain the fuel or use a fuel stabilizer. It will help start your generator when you need it fast.

Previous articleTop 5 Compact 1000 Amp Jump Starters that can Start Anything 2024
Next articleAll you need to know about starter fluid alternatives & how to use them.


Please enter your comment!
Please enter your name here