You’re most likely without a power source when you’re trying to start your generator. That can make it increasingly frustrating when it just won’t start.
A generator won’t start when it isn’t getting sufficient fuel, air, and spark.
This may be due to a plugged air filter, wrong choke setting, faulty on/off switch, empty fuel tank, plugged fuel filter, clogged fuel line, dirty carburetor, bad spark plug, bad spark arrestor, low engine oil, or faulty fuel cap.
Check the battery, starter solenoid, and ignition switch on models with an electric start.
Place the generator on a flat-level surface, remove the spark plug wire, and wait for the engine to cool prior to performing repairs. Refer to your generator operator’s manual for safety precautions.
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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 For Your Generator Starting Problem
1. Empty Gas Tank
A generator without enough gas in the fuel tank will fail to start. I’m sure you already know this. I only mention it here because you may have skipped over the obvious items.
You may have developed a leak and are going through more fuel than usual. You may also have a faulty fuel gauge.
SOLUTION: If you are out of gas, check for fuel leaks or a faulty fuel gauge. Make any necessary repairs. Add fresh gasoline to the fuel tank. (If your generator uses a 2-cycle engine, fill it with a fuel mix of gas and oil).
2. Bad or Old Fuel
Old gas is often the primary cause for a generator to stop running. Gas doesn’t stay good for very long and can begin to break down as soon as 30 days after purchase.
Ethanol, used in most gasoline, attracts moisture to the fuel system. As this ethanol and water mixture leaves behind a varnish that can cause component failure and fuel restrictions.
This mixture will also separate from the gas and sinks to the bottom of the tank. It is highly corrosive.
Because of the adverse effects ethanol has on a 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 generator, drain the fuel using a fuel siphon pump. Mix fresh fuel with a fuel additive to help clean the fuel system, reduce moisture, and stabilize the gas.
- 2-cycle engine: Requires a gas and 2-cycle oil mixture.
- 4-cycle engine: Requires straight gas.
Add the fuel 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.
3. Plugged Fuel Filter
You may find a fuel filter in the fuel tank or installed between the fuel lines on some generators. On other models, a fuel sediment bowl and screen will be installed that will need to be removed and cleaned.
The filter or sediment bowl and screen are used to keep dirt and other contaminants from entering the fuel system causing wear on the engine.
A plugged filter or screen will prevent a good flow of fuel from getting to the engine for combustion.
SOLUTION: Replace a plugged fuel filter or clean the fuel bowl and screen.
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
Air, fuel, and spark are used to form an explosion in the cylinder to start the engine. The carburetor is the component that is responsible for regulating the amount of gas and air introduced to the cylinder for combustion.
When the carburetor fails because the fuel passageways become clogged from old fuel, gas isn’t able to get to the cylinder and the generator won’t start.
SOLUTION: Once you have verified you are getting gas to the carburetor, but not getting gas to start the generator, remove the carburetor.
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
The air filter is another maintenance part installed to keep dirt and debris from entering through the air intake. It only takes a small amount of dirt to cause engine damage.
You must always run an air filter on your generator. This filter should be checked several times throughout the year to clean it and ensure it is in good condition.
I recommend starting each year out with a new air filter. Maintenance doesn’t stop there. The filter needs to be regularly checked and cleaned to keep it in good condition.
A very dirty filter not only may keep the generator from starting, but it can also cause it to overheat and potentially cause permanent engine damage.
SOLUTION: If you find your air filter is plugged, clean a foam air filter with mild detergent and water. Squeeze excess water out of the filter and allow it to air dry.
Some foam air filters require the filter to be lightly saturated in clean engine oil to help trap the dirt while others do not require oil. Refer to your operator’s manual if you are unsure of the requirements for your type of foam filter.
If you have an air filter that is dark in color, damaged, or torn, replace it with a new air filter.
If your generator uses a paper filter, replace it with a new filter once a year and more often when used in dusty conditions.
7. Plugged Fuel Vent
The fuel tank vents out of the gas cap or another part installed on top of the fuel tank. 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 fuel tank vent, the fuel tank will form a vacuum as fuel is consumed from the tank. This prevents fuel from getting to the carburetor and your generator will fail to start.
SOLUTION: To determine whether your gas cap is the cause of your starting problem, loosen or remove the cap to allow air inside the tank and then attempt to start the generator.
If it starts but stops running again after you have the cap tightened and allow it to run for a while, you may have a problem with the vent. I recommend replacing the fuel tank vent.
8. Plugged Spark Arrestor
The spark arrestor screen is a metal screen on the muffler that prevents sparks and hot exhaust 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 because it can’t exhaust hot air.
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 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 it is dirty, the porcelain is cracked or the electrodes are pitted. 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 if the spark plug is in good condition and just a little dirty. However, if your spark plug tip is very dark in color or damaged, you must replace it with a new one.
The 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 ohmmeter. If you find a break in the continuity, replace the ignition coil.
11. Incorrect Engine Oil Level (4-cycle engine)
A 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
Some generator models use a dial or switch. It may be faulty and no longer functions 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 generator models will use a choke lever or knob 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. Check for a stuck choke plate that may be preventing the generator from starting with the dial or manual choke lever in the correct position.
13. Bad Recoil on a Manual Start 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 on an Electric Start Generator
The ignition 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 on an Electric Start Generator
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 on an Electric Start Generator
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 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.