A Generac generator won’t stay running and will keep shutting off when there is a lack of air or fuel flow to the engine; the low engine oil sensor is triggered, or the generator is overloaded.
This may be due to a dirty air filter, incorrect choke setting, empty fuel tank, plugged fuel tank vent, dirty carburetor, low engine oil, faulty ignition coil, or too many electrical items plugged into the generator.
Don’t forget to remove the spark plug wires and wait for the generator to cool down before performing any repairs. Follow additional safety precautions found in the operator’s manual.
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Follow all safety instructions provided in your equipment operator’s manual prior to 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.
6 Reasons a Generac Generator Won’t Stay Running
The generator requires air, fuel, and spark to keep running. Without any one of these items, it will shut down. To determine the root cause you must look at items that may restrict air, fuel, or spark after it starts running.
You will also need to ensure the engine oil level is correct and you are only powering items your generator can handle so you don’t overload it.
1. Too Much Load for the Generac Generator Size
When the generator is attempting to power items greater than its load limit, it will shut down and not continue to run. To make sure you don’t put too much load on your model Generac generator, check its load limit.
Next, add up the wattage requirements of the items you are running at one time using the generator. The wattage for the items must add up to less than the generator’s load limit.
Follow these tips to determine the wattage capacity:
- You will find the wattage of most electrical items listed on a tag attached to the item.
- Some motors require additional wattage to start an item. In this case, the starting wattage should be used when calculating wattage requirements.
- Add the wattage of all items that will be plugged into the generator at one time to get a total.
- This total wattage must be less than the generator’s wattage compacity.
2. Lack of Air in the Generac Generator
Dirty Air Filter
The air filter can become plugged when it isn’t cleaned or replaced regularly. A clogged filter can keep the engine from getting sufficient air to stay running.
Remove the filter and inspect its condition. Replace the filter with a new one when the filter is damaged or very dirty. Clean it if it is in good condition, but just a little dirty.
Incorrect Choke Setting
The choke is used to restrict air when starting a cold engine. When the engine warms, the choke must be placed in the off position so the warm engine gets enough air to continue to run.
If the engine shuts down right after starting, It may be due to an incorrect choke setting or the choke may be stuck in the closed position. When starting a warm engine, the choke should be placed in the run/open position so it continues to run without shutting down.
3. Lack of Fuel in the Generac Generator
Empty Fuel Tank
This is an obvious reason why a generator will shut down, but sometimes one forgets the last time fuel was added to the tank. It may also be due to a fuel leak or a bad fuel gauge.
Add fresh fuel to the tank. Fix any fuel leaks and replace a bad fuel gauge if you find either of these problems.
The carburetor regulates the amount of fuel that is mixed with air to form combustion. Over time, old gas can leave a coating that causes the carburetor to stop functioning properly so the engine doesn’t receive the gas it requires to keep running.
When this happens, the carburetor must be removed from the generator and cleaned using carburetor cleaner to remove the crusty buildup left behind by old fuel. I find it best to take photos as I take apart a carburetor so it is reassembled right.
If you don’t want to tackle cleaning the carburetor or you can’t get it cleaned and working again, replace it with a new one.
Plugged Fuel Tank Vent
Generac generators use either a vent located in the fuel cap or a vent located on top of the fuel tank. The vent can become plugged so the air isn’t able to pass through the vent to equalize the pressure in the tank to the atmospheric pressure.
When the fuel tank isn’t able to vent, it forms a vacuum keeping fuel from getting to the carburetor. This can cause the generator to stop running. The vent may be the problem when the generator won’t restart until the gas cap is loosened so air is able to enter the tank.
4. Lack of Spark in the Generac Generator
Bad Spark Plug
A fouled spark plug can cause an intermittent spark that may cause the engine to run rough and die. In addition to a bad spark plug, loose spark plug wires or an incorrect electrode gap can also cause this problem.
Clean a dirty spark plug using a wire brush. However, if you find the spark plug is damaged, worn, or very dark in color, you must replace it with a new spark plug.
Bad Ignition Coil
The ignition coil can separate and short out when the generator gets hot. This will result in the spark plug not being able to create a spark because it isn’t getting the voltage it needs.
First, make sure the spark plug is in good condition. Next, check the continuity using an ohmmeter. Replace it if you find a break in the continuity.
5. Low Engine Oil Level in the Generac Generator
When the engine oil level is too low, the Generac will shut down to protect the engine from damage. Ensure the generator is on a flat level surface before checking the oil level so you get an accurate reading.
Check the oil level using the oil dipstick attached to the oil cap. When you find the level is too low, add oil until it is at the correct level according to the dipstick.
If you find you have the correct engine oil level and the low oil sensor light stays on, you may have a faulty sensor.
6. Pugged Spark Arrestor on a Generac Generator
A spark arrestor screen is placed on the muffler to prevent hot exhaust material from shooting out of the muffler and possibly causing burns or fires.
When hot air from the engine isn’t able to exhaust because of a plugged spark arrestor screen, it will bog down and may shut off.
Remove the spark arrestor screen and clean it using a solvent or a small metal brush. If you find it has a hole in it or is damaged, it must be replaced with a new screen.