I keep a few different generators on hand to power my house, for emergency use during a power outage, and for my fall football tailgates.
For me, they are a necessity to keep in good working condition in the event of a power outage so I can’t procrastinate resolving a starting problem.
A Generac generator won’t start due to an empty fuel tank, old gas, plugged fuel filter, clogged fuel line, dirty carburetor, bad spark plug, faulty ignition coil, plugged air filter, plugged spark arrestor, incorrect engine oil level, bad dial, faulty starter recoil, or bad starter switch.
Take caution when making repairs on your equipment to prevent injuries. Remove the spark plug before performing repairs and wait for all parts to cool down.
Follow all safety guidelines found in the operator’s manual.
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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
Reasons Your Generac Generator Won’t Start
1. Empty Fuel Tank
A generator has a small fuel tank. You may have forgotten the last time you added fuel or your fuel gauge no longer works and provides you with a sufficient reading.
I only mention this obvious cause of a starting problem because it’s easy to skip checking the fuel level when you’re frustrated.
SOLUTION: Add fresh gasoline to the fuel tank.
2. Bad or Old Fuel
Many people don’t realize gas degrades and starts to become less effective as it sits for long periods of time. This can begin to happen as soon as 30 days after purchase.
Ethanol, found in most gasoline, attracts moisture to the fuel system. As this ethanol and water mixture evaporates it leaves behind a varnish that can cause component failure and fuel restrictions.
Because of the adverse effects ethanol has on a Generac generator, it’s important to keep these things in mind when purchasing, storing, and consuming fuel:
- Purchase fresh fuel with a minimum 87 octane rating (91 RON).
- Never use gas with more than a 10% ethanol content. Ethanol-free fuel is best.
- Consume fuel within 30 days.
- Use a fuel stabilizer if you are unable to consume it within 30 days to make it last a little longer without breaking down. (Fuel stabilizer must be added to fresh fuel. It will not reverse the effects of old fuel).
- Store fuel in an approved fuel container away from moisture or combustible products.
SOLUTION: If you find old fuel in your Generac generator, drain the fuel using a fuel siphon pump. Mix fresh gas with a fuel additive to help clean the fuel system, reduce moisture and stabilize the gas.
Add the gas to the fuel tank. Once you are able to get the generator to start, allow it to run for about 15 minutes so the gas and stabilizer mixture is able to work its way through the fuel system.
I like a product called Sea Foam Motor Treatment. I use this product in every tank of gas to help reduce the issues that can result from using fuel with ethanol. Another good option is STA-BIL.
3. Plugged Fuel Filter
A fuel filter is used to strain fuel as it comes out of the fuel tank to keep dirt and debris from entering the fuel system causing wear on the engine. When this filter isn’t replaced regularly or you placed dirty fuel in the tank, it can become plugged.
This will cause less fuel to be able to pass through the filter so the engine doesn’t get the fuel it needs to start and continue to run.
I recommend replacing the fuel filter annually for the average homeowner. If you are using your generator more often than 300 hours a year, you should replace it more frequently.
SOLUTION: Replace a plugged inline fuel filter. You will find an arrow on the side of the new filter indicating the direction it must be installed. Install the filter with the arrow pointing in the direction of the fuel flow.
4. Clogged Fuel Line
The gummy deposits or dirt left behind by old fuel can clog the fuel system including the fuel line. Check for clogs in the fuel line that could be restricting fuel to the engine.
SOLUTION: If you find a restriction in the fuel line, remove the line from the generator. Spray carburetor cleaner to loosen the clog and blow compressed air to the line to remove it.
If you are unable to remove the fuel restriction, replace it with a new fuel line.
5. Dirty Carburetor
The carburetor’s function is to regulate the amount of gas that is mixed with air to form combustion in the engine cylinder.
When the carburetor is dirty and gums up from old fuel, components in the carburetor no longer function properly. The carburetor may not allow the gas required to start your Generac generator.
After you have verified you are getting fuel to the carburetor, you need to take a look at the carburetor. This is a common part that can gum up and leave behind crusty deposits from old gas.
SOLUTION: Remove the carburetor and clean it with a carburetor cleaner to remove varnish and deposits forming in the carburetor.
Take a look at the carburetor float, float needle, and fuel jets to make sure they are sufficiently clean and in good condition.
If you find any damaged parts, you must replace them using a carburetor rebuild kit or a replacement carburetor.
6. Plugged Air Filter
Like the fuel filter, the air filter is installed to keep dirt and debris from entering through the air intake. This is to protect the engine from damage that can be caused by just a small amount of dirt.
You must always run an air filter on your generator. You must check the filter several times throughout the year to clean it and ensure it is in good condition.
For the average homeowner, I recommend replacing the air filter annually and cleaning it a few times a year.
When you notice the filter is extremely dirty or damaged, you must replace it. You will definitely need to replace it more often if you are running the generator in dry dusty conditions.
If you are not cleaning and replacing the filter regularly, the filter can become plugged with so much dirt that the engine won’t get sufficient air. It can overheat and cause extensive permanent engine damage.
SOLUTION: If you find your air filter is plugged, you must clean it using the procedure below for your type of air filter. If you are unsure of the type of filter you have and its cleaning procedure, consult the operator’s manual.
Clean a Generac generator foam-style air filter
- Remove the air filter from the housing.
- Wipe out any dirt remaining in the air filter housing and cover. Don’t allow dirt to fall into the air intake.
- Inspect the foam filter for damage and replace it if needed.
- If the filter is in good condition, clean it in soapy water and rinse it until the water runs clear.
- Squeeze the filter and allow it to dry.
- Install the air filter.
- Reattach the air filter cover.
Clean a Generac generator paper air filter:
- Remove the air filter from the housing.
- Wipe out any dirt remaining in the air filter housing and cover. Don’t allow dirt to fall into the air intake.
- Inspect the paper air filter. Tap the filter to loosen dirt so it falls from the filter. If the filter is very dirty, damaged, or no longer seals the air intake sufficiently, replace it with a new one.
- Install the air filter.
- Reattach the air filter cover.
7. Plugged Fuel Vent
On most portable Generac generators, the fuel tank vents out of the gas cap. A vent is required to keep the pressure in the fuel tank equal to the atmospheric air pressure.
When air isn’t allowed to pass through the gas cap due to a plugged vent, the fuel tank will form a vacuum. This prevents fuel from getting to the carburetor and your generator will fail to start.
If your generator fuel cap has a lever on the cap showing an on and off position, make sure the lever is placed in the on position when starting and running the generator.
On some Generac generators, an independent fuel tank vent may be located on the top of your fuel tank.
SOLUTION: To determine whether your cap is the cause of your starting problem, loosen or remove your cap to allow air inside the tank and then attempt to start the generator.
If it starts, but stops running again after you place the cap back on the generator and allow it to run for a while, you may have a problem with the cap. I recommend replacing a bad fuel cap or bad vent.
8. Plugged Spark Arrestor
The spark arrestor screen is a metal piece on the muffler that prevents sparks and hot material from emitting from the muffler.
This screen is required to prevent injuries and fires. When it becomes plugged, the generator will have a hard time starting and running.
SOLUTION: Remove the spark arrestor screen from the muffler. Take a look at it to ensure it isn’t torn and doesn’t have any holes in the screen. If it does, the screen must be replaced with a new one.
If it doesn’t have any damage, go ahead and clean it with a commercial solvent or brush it lightly with a small metal brush to remove soot deposits. Once clean, reinsert the screen back onto the muffler.
9. Bad Spark Plug
A spark plug can be faulty when the tip is dirty, the porcelain is cracked or the electrode is burnt. This will cause your generator not to start because of a lack of spark.
SOLUTION: You can clean the spark plug to remove the deposits on the tip. If your spark plug tip is very dark in color or damaged, you must replace it with a new one.
Your spark plug needs to be properly gapped following the manufacturer’s specifications as found in the operator’s manual. Starting problems can be caused by a spark plug that is gapped incorrectly or a spark plug wire that is loose.
10. Bad Ignition Coil
Before checking for a bad ignition coil, make sure your spark plug is in good condition. The ignition coil provides voltage to the spark plug so it can start the engine.
If the spark plug isn’t able to fire due to a bad spark plug or ignition coil, the engine will not start.
SOLUTION: Check the continuity of the ignition coil using an ohm meter. If you find a break in the continuity, replace the ignition coil.
11. Incorrect Engine Oil Level
The generator will not start when the engine oil is not at the correct level. The generator has a sensor that recognizes a low engine oil level. It will prevent the engine from running with a low engine oil level.
SOLUTION: To check the engine oil level, begin by placing the generator on a flat-level surface. Remove the oil fill cap and wipe off the dipstick with a clean cloth to remove the oil.
Reinsert the dipstick into the oil-fill tube, but don’t screw on the cap. Remove it and look at the oil level on the dipstick. Ensure it is in the full range on the dipstick.
If it is not, correct the engine oil level by removing or adding a little oil until it is at the correct level.
When you find you have the correct engine oil level and the low oil sensor stays on, you may have a faulty sensor. It’s best to take the generator to a service center to be repaired.
12. Bad Choke Dial/Switch or Wrong Choke Setting
The OFF-ON-CHOKE dial or switch may be faulty and no longer function correctly.
This bad dial or switch on a generator will keep the generator from starting if it is no longer adjusting the choke when switching it between the choke/start and on positions.
Other Generac generator models will use a choke lever to manually adjust the choke. In this case, the choke lever must be placed in the choke position to start a cold engine.
It will then need to be adjusted to the off position so the engine receives enough air to keep running.
SOLUTION: Have a service center identify if the problem is in the dial or another problem such as a stuck choke that is preventing the generator from starting with the dial in the right positions.
If you have a manual choke lever, make sure it is placed in the correct position to start the engine.
13. Bad Recoil on a Manual Start Generac Generator
When the starter recoil wears or parts of the recoil break, it’s hard or impossible to get the generator started. The rope on the recoil can become unstrung or the pulley, springs, or clips may break causing your starting problems.
SOLUTION: Sometimes, restringing the recoil is all you need. Other times you will have to replace broken parts in your recoil. Before replacing parts, price out a full recoil replacement.
Depending on the price difference, it may be better to replace the recoil assembly over tearing it down and replacing broken components.
14. Bad Ignition Switch (Electric Start)
The switch can go bad on a generator with an electric start preventing it from starting. When the electric start isn’t working, use the manual recoil to start the generator until you are able to get it fixed.
SOLUTION: Test the switch using a multimeter and replace it if necessary.
15. Bad Battery (Electric Start)
Make sure the battery is charged. If it has a low charge, you can attempt to charge the battery. If it won’t hold a charge, it’s time to replace the battery with a new one.
Check the cables and wiring to make sure you have good continuity and making good connections.
SOLUTION: Check the voltage of the battery and charge it if it is weak. Replace a dead battery or one that won’t hold a charge.
16. Bad Starter Solenoid (Electric Start)
You may hear a clicking or humming sound when you press the ignition switch button or turn the key (depending on your model) and your generator won’t start. Or, you may find the wiring is getting hot and beginning to smoke.
These are indications the solenoid may be bad. A starter solenoid goes bad when the internal spring gets weak or the copper plate begins to corrode.
A weak starter, bad battery, or bad ground can also be the reason for the solenoid failure.
SOLUTION: You can attempt to bypass the starter using a screwdriver or pliers by touching the cable from the battery and the cable to the starter.
Be careful as it may throw a spark. If the engine turns over with the solenoid bypassed, it is likely the starter solenoid is bad.
You must check for loose wires or bad ground before replacing the solenoid. These are items that can cause the solenoid to not work correctly.
The good news is most portable Generac generators with an electric start have a manual starter recoil installed to pull-start it to get it running. If you are able to manually start it, you can narrow down your problem to the electric start system.