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Generator Starts then Dies (won’t Stay Running)


Many things could prevent your generator from running and that includes running out of gas! Also, if you forgot to drain your gas before storing the generator and you kept it in a garage for more than a month, you may have a problem with a sticky (gummy) fuel that now clogs your gas tank, gas pipes, carburetor, and injectors.

Your brand new generator should not have this problem, but don’t forget that they do not get shipped with oil and there is a certain way to get turned it ON (so it stays running)!

Here are the basic steps for making new generator work and avoid trouble. If you missed any of those, your generator will not run properly, or worse – overheat!

  1. Add oil
  2. Add gasoline
  3. Turn breaker OFF
  4. Turn gas valve ON
  5. CLOSE choke
  6. Start generator
  7. OPEN choke
  8. Turn breaker ON
  9. Connect equipment

Of course, things happen and we can be in a hurry and do not store a generator properly! Here are some steps for making an old generator work (if you have stale fuel inside):

  1. Clean carburetor
  2. Clean fuel tank and gas lines
  3. Clean fuel cap
  4. Replace fuel filter
  5. Clean or replace an air filter
  6. Check oil levels and pressure
  7. Check coolant levels and refill if necessary
  8. Make visual inspection (look for frayed wiring and worn out connections )
  9. Check for leaks (hoses, fittings, and connections)
  10. Check that your battery is full and not corroded
  11. The rest – same as above (except, you don’t add oil unless you don’t have enough).

Let’s say you took your time to drain fuel before storing and do not have a clogging issue. Here is what you should check on an old (properly stored) generator to make sure it works after you start it:

  1. Check fuel filter (replace if necessary)
  2. Check an air filter (replace or clean if necessary)
  3. Check oil levels and pressure
  4. Check coolant levels and refill if necessary
  5. Make visual inspection (look for frayed wiring and worn out connections )
  6. Check for leaks (hoses, fittings, and connections)
  7. Check that your battery is full and not corroded
  8. The rest – same as starting a brand new generator (except for the oil, unless you don’t have enough).

After starting your older generator, it’s also a good idea to listen for unusual noises and vibrations as it runs. If your generator detects something wrong (via a sensor, in the newer models), it may shut down because of that, to prevent further damage to the equipment and possible hazard to your health.

Before we start doing further troubleshooting and figure out why your generator dies after starting, you did not forget to REFIL your fuel tank, did you?

Just like a car, it will not go far without enough gasoline to support it! If so, just refile and you are good to go!

** Important! Wait until the generator cools down to fill up the tank.

If all simple solutions are taken care of (choke lever is in the proper position and fuel tank is FULL), then you will need to check the following:

  • Fuel delivery problem
  • Air obstructions
  • Overload problem

The most common cause for generator shutting down after it starts is the clogged carburetor (with old, sticky fuel that was left inside for an extended period of time).  This sticky substance will clog the carburetor’s jets and ports, preventing the engine from working.

If the carburetor is clogged, you can use carburetor cleaner to clean it (instructions below). In case cleaning the carburetor does not work, the carburetor should be rebuilt by a professional or replaced entirely.

Make sure that after the cleanup, replace your fuel with the freshest possible along with a fuel stabilizer. Next time NEVER put your generator in storage with fuel inside!

There are also instances when the generator is not receiving enough fuel due to a clogged fuel filter, and your generator can’t receive enough of it to keep running. A dirty fuel filter can cause stalling after the generator has been started.

The fuel valve controls the fuel flow to the engine. If your generator stops working after a while, it might be due to a clogged fuel valve. In this case, you may need to replace the fuel valve.

A fuel cap may also cause problems if it’s too tight or clogged. The air will not be able to flow into the tank and therefore will create a vacuum in which fuel cannot come out (eventually forcing a generator to shut down).

You can also try using motor treatment foam (if you run out of ideas) that will liquefy gum and varnish deposits along with internal engine impurities. One of them is called a Sea Foam (paid link) and you can conveniently purchase it on Amazon.

A dirty, filthy air filter (like a clogged fuel filter), can prevent enough air from reaching the generator’s motor and that may cause your generator to stop working. Your small engine may also stall because of the vapor lock, which develops when the fuel overheats and vaporizes too rapidly.

Make sure there’s adequate oil in the engine and on the flip side, make sure that the reservoir is NOT overfilled:

Since oil serves as both a lubricant and a coolant, if the temperature in the engine rises too high owing to a lack of oil, the generator is likely to shut down. In case of too much oil, the circulation may not be smooth enough to adequately lubricate the components of the generator’s engine.

Also, if your generator is equipped with a LOW OIL sensor, it may shut down your generator upon detecting this problem. This brings us to our next point…


Generators are getting smarter and smarter, therefore keep you a lot safer than they did before! They have different sensors to prevent potentially small problems from turning into catastrophic situations and this means:

“If one of those sensors is triggered, your generator is going to shut down!”

Also, if your sensors start to fail (due to some electrical malfunction), it may result in the generator shut down.


Your choke could be in the wrong position and this is why your generator is shutting down. It is an important part of starting your generator properly and an easy one to miss or confuse the labels:

Before starting the generator, make sure the choke lever is in the CLOSED/ON position. You’ll need to turn the chock lever to the OPEN/OFF position as soon as the generator starts operating.

If you forget to do so, the generator will operate for a short time before shutting off.

Common reasons behind generator stalling

1. Vapor lock

Sometimes in hot weather (above 97-98 degrees F), your generator will develop something called: “a vapor lock”. This is when the gasoline in a fuel pump vaporizes and the pump begins to push gas (or vapor)!

When the flow of fuel to the carburetor is cut off, the engine will stall. The main symptom of the vapor lock is:

“The engine operating fine for a while before stalling and restarting only when it cools down”

Carbureted and air-cooled engines are particularly vulnerable to this problem, especially on hot summer days. When the gasoline (the most common type of fuel with this problem) in the fuel delivery system overheats and vaporizes too quickly, vapor lock develops.

The extra gas bubbles that arise build up to the point where they obstruct the regular fuel supply. Some generators utilize a gasoline pump that is Vapor Lock Resistant. Here is a nice video on how to “cure” vapor locks:

How To PREVENT VAPOR LOCK In Your GENERATOR, Small Engines, And Carbureted Classic RV Or VAN!

There are several things that you can do to avoid vapor locks:

  1. Use fresh fuel with a fuel stabilizer at all times. In as little as 30 days, gasoline may get stale. It is recommended to add a fuel stabilizer whenever refilling with gas. Fuel stabilizer additives may be found at most auto parts stores.
  2. Use ethanol-free fuel. Avoid using gas that has been combined with alcohol or ethanol whenever possible. These mixed fuels are developed primarily for use in automobiles and are not advised for use in smaller air-cooled engines.

Keep in mind that chances of developing a vapor lock rise if you are operating your generator at high temperatures or altitudes. Your generator could also overheat in exceptionally high temperatures during prolonged usage. In this high-risk situation, use caution and take pauses with using your generator.

You should also make sure you’re using the appropriate grade of oil and that the fuel filter is clean. SAE 30 is the most common oil used for 4-stroke generator engines.

2. The fuel system problem

Not all fuel components burn effectively and as the more volatile components evaporate, old fuel degrades. This can result in residual build-up inside the fuel delivery system.

In certain situations, totally emptying the fuel system and replacing it with new gasoline can solve the problem. Carburetors that have been clogged with old gasoline must be properly cleaned or replaced.

You can clean a carburetor with a special carburetor cleaner (paid link) that could be easily purchased from Amazon as well! Here is a good explanation of how to clean a carburetor:

How to Clean a Generac Briggs and Stratton Nikki Carburetor - Generator Hunting for Fuel

To replace gaskets and other components, you may need a Carburetor Repair Kit (available on Amazon, paid link):

Replacing your carburetor may be necessary if cleaning is not working out for you or is too troublesome. They are quite affordable, and maybe it’s a better idea to replace the whole thing than to clean it piece by piece.

Not to mention, the engine performance can be improved by purchasing and installing a new carburetor! They also come in kits with cleaning supplies and mounting gaskets (only make sure you get one suited for your specific generator model). Here are some carburetors for you:

Your fuel tank may need a really good cleaning and here is how you do it:

  1. Mix 1 cup baking soda and 2 cups white vinegar.
  2. Add this mixture to your gas tank.
  3. Fill three-quarters of your gas tank with water to create a cleaning solution.
  4. Wait for at least 1 hour for accumulation breakdown (the mixture can be left in the tank overnight for a thorough clean).

If the fuel valve is clogged or closed, your generator will run out of gasoline and shut down. If the generator shuts down due to a closed fuel valve, just open it and restart the engine:

When the engine is turned off, the valve should be in the OFF (or CLOSED) position. When the engine is turned on, it should be in the ON (or OPEN) position:

If the engine is a diesel, prime the air out at the fuel valve before restarting it with the valve in the OPEN position. The clogged fuel valve needs to be cleaned or replaced.

Small engine fuel filters also need to be examined and replaced if unclean. They are generally fastened with hose clamps along the fuel line between the fuel tank and the carburetor:

Also, you should watch out for leaks in valves, gaskets, or pipes.

3. Cooling system problem

Ensure that air intake and cooling fins are cleaned on a regular basis. Maintaining the cleanliness of these airflow regions will aid in keeping the engine as cool as feasible.

Here is how you change an air filter on your generator:

If after cleaning your generator properly, you are still not sure what is going on, then you might simply have an overload problem. The best part? It is not complicated to solve:

“All you have to do is reduce the load!”

It is very common that the generator’s circuit breaker will trip if you use it over its maximum capacity, or the “overload light” will come on and the generator will shut down. Why is this important?

Just like breakers in your own house, overload shutdown will not allow your generator to produce more electricity than it’s supposed to, therefore preventing overheating and very dangerous fire hazard situation.

If you realized that you overloaded the circuit or the light (overload notification) came on, just disconnect all the appliances and hold a reset button for about a minute.

When the indicator goes back to normal, just reconnect fewer appliances and try again. It may be a good idea to actually CALCULATE how much are you loading on your generator! If wattage is not mentioned, multiply VAC by Amps:

Also, don’t forget about surge ratings (or starting watts) and make sure that your generator can actually handle the demand of your equipment:

In case you do not know if you’re overloading your generator, here are few ways to determine it (in case breakers don’t’ work or overload light doesn’t illuminate):

  • Overheating. Your generator is overworking, therefore more heat is produced.
  • Noise. Your generator is trying twice as hard to keep itself cool and the noise is coming from fans.
  • Soot. If you notice extra soot in your exhaust, then the generator may be overloaded.

It is always bad if the circuit breaker does not trip when the generator becomes too hot! The generator consists of a very flammable material (fuel) inside a compartment that could burst if under a lot of pressure and you can only imagine the consequences…

Overloading is a common problem with an easy solution, so before you start disassembling everything, try disconnecting any unneeded devices to see if it fixes the problem. Once the generator is reset properly try connecting devices one at a time for the best result.

5. Malfunctioning spark plug

The spark plug’s job is to ignite the gasoline and air mixture, resulting in an explosion that drives the piston downward. If the edge of the spark plug has dirt on it, no spark will be produced, and the combustion process will fail.

This problem can arise at any point during the engine’s operation. Spark plugs can also short-circuit and fail to generate the necessary spark. After removing the spark plug from the generator, look for dirt and debris.

They are not expensive and may be easier to replace than to clean:

You can purchase and install a new plug if the current one is weak or not working properly (only make sure you choose the same type of spark plug as the one you took out in terms of voltage).

6. Exhaust system blockage

If the smoke is not removed from the system, the generator will not be able to run since it can’t burn any more gasoline. The smoke generated by the engine must be removed from the engine after combustion in order for the generator to continue working.

If you notice that the amount of smoke produced is lower than usual, you need to check the exhaust system all the way to the combustion chamber.

7. Electrical problems

The generator’s wiring and current flow from the battery to the components may have problems, causing it to shut down. If there is a problem with wiring or battery connections, there will be no ignition and the rest of the system will not function properly.

Consult a certified professional to solve wiring and connection problems.

8. Engine problem

Now, the hardest problem of them all! That is when the engine fails and all you can do is take it to the repair center! Fixing engines could be expensive and sometimes it makes sense just to get a new generator.

Click on the white button above to find your electrician!

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