Well, what do you know?  Your plans for taking advantage of a nice sunny day to get some lawn maintenance done were going so well until the moment your strimmer didn’t start.

After all, the lawn is nice and mowed.  Looks great, right?  Except for some edging work and areas too small or awkward for the mower to reach.  That’s where your strimmer was supposed to come into play.

Supposed to.

Instead, though, you’ve got a strimmer that won’t start.  Maybe you’ve even got a strimmer you’ve recently replaced the fuel filter and air filter on.  Maybe you’ve even got a full tank of gas.

So, why won’t it start?

Often times the simplest answer is the most common.  In this case, let’s assume your strimmer’s engine is simply flooded.  This could be a onetime thing or maybe it’s been flooding consistently for a while.

In either case, there are, thankfully, some quick fixes you can try out to see if you can get that engine up and running without having to do too much work.  That way, your strimmer is back to working for you like it was designed to.

1.  What is a Flooded Engine?

Before getting too much further down the path toward a resolution to your flood engine, let’s examine what’s meant by flooded.

First off, it doesn’t mean your strimmer was washed away or submerged in a storm or flooded river.  Nor does it have anything to do with ocean surge.  All of those can easily damage or destroy your strimmer’s engine (especially if salt water’s involved) but this isn’t the type of flood referred to here.

No, a flooded engine is simply an internal combustion engine that’s been fed a fuel-to-air mixture that’s too rich in one of those items and thus prevents ignition.

To put it another way, the fuel/air mixture released into the combustion chamber doesn’t explode to provide self-sustained engine rotation.  Instead, the mixture just sits in the chamber.

If you continue to try and start the strimmer without correcting this issue, more and more non-ignited fuel adds up, flooding the engine.

Strimmer On The Ground With Flooded Motor
An engine in this condition will not start until the excessively rich mixture has been cleared.

2.  Old Gas

Yes, you’ve got a full tank of gas.  But how old was that gas before filling your strimmer?  Or how long has your strimmer been sitting, unused, with a full tank?

Has the fuel been sitting in a gas can in the garage or shed for a while?  Has it been exposed to temperature changes that may have increased evaporation within the can or even condensation?

Or was it just plain old gas and probably shouldn’t have been used in the first place?

Is that enough questions?!?!

Old gas can negatively affect combustion as well as performance.  Remember, besides the possible presence of water building up in older gas, you also have to take into account the intrusion of other contaminants.

When added to an engine, old gas can lead to internal corrosion of your equipment, damage, and incomplete to non-existent combustion.  This is where you might be keeping the choke on or pressing the priming bulb repeatedly in an attempt to get that engine running but failing.

Instead, what you’re succeeding at is flooding the engine.

So, in this example, you’re not necessarily getting a fuel/air mixture that’s too rich.  Instead, you’re getting old gas that won’t ignite even if the ratio was perfect.  And to try and get it to ignite, you keep pumping fuel in.

The fix is to clear out the old gas and refill the strimmer with fresh fuel.

3.  Wet Spark Plug

Keeping the choke on or continuously pushing the priming bulb can result in a carburetor with too much fuel built up in it and a flooded engine.  With that fuel built up in the carburetor, you might also have to deal with a wet spark plug.

A spark plug that gets soaked with fuel won’t spark correctly.  If this is the case, even if you clear the flooded condition, you still won’t get any or adequate enough spark to ignite fuel.

The fix in this case is to either allow enough time for the spark plug to dry, or remove it and clean it.

Or, you can just replace the plug altogether if it’s old or if cleaning doesn’t work.

4.  Take Another Look at Your Fuel and Air Filters

Yes, you may have recently replaced your fuel filter or air filter or both.  This doesn’t mean you shouldn’t check them again.  This is true if you use your strimmer often or rarely.

Here are a few reasons why.

  1. If you use your strimmer all the time and you’ve been having flooding problems, that means you’ve been try to crank the engine over often and failing.  Even if it hasn’t been running, those filters have been filtering every time you’ve attempted to start the engine.  Just do a visual inspection.  Worst case, you replace them and move on.
  2. If you hardly use your strimmer, how new is new?  Yes, the strimmer hasn’t been used much but it doesn’t mean the filters are fresh out of the box.  Again, do a visual inspection and replace if necessary.

Just remember, if you do have filters that are clogged or damaged, it can result in your fuel/air mixture being overly rich and lead to engine flooding.  The fuel doesn’t have to be old nor does the spark plug have to be wet in this case.

The great thing about fuel and air filters for small internal combustion engines is they’re inexpensive, easy to replace, and a very quick fix.

5.  Take a Look at Your Carburetor

The carburetor is responsible for ensuring the fuel/air mixture is correct for internal combustion.  If something’s wrong with it, that ratio can easily get thrown out of whack and result in flooding.

If you’ve put in clean new gas, cleaned or replaced the spark plug, and ensured the filters are good to go, take a look at the carburetor.  Often, it may require some cleaning with carburetor cleaner and possibly gasket replacements.

It’s recommended to follow your manufacturer’s recommendations and it wouldn’t hurt to have a carburetor rebuild kit handy in case you do need to replace some parts like gaskets.

Hand Holding Strimmer Carburetor
The function of the carburetor is to mix a mist of gasoline and air together to form an explosive mixture, which is burned in the cylinder of the engine.

6.  Steps to Correct a Flooded Engine

Besides addressing possible issues with the age of your gas, the condition of your spark plug, filters, and carburetor, there’s still the issue of how to clear a flooded engine.

So, why not cover this first?  Well, if your strimmer is constantly flooding, there’s probably an underlying issue behind that, which has been covered.  Better to understand the why the engine may be flooding before getting to the exact procedure for how to clear it out.

Plus, it’s a great way to close out an article on flooded engines!

  1. Set your ON/OFF switch to ON (or RUN, if that’s what your strimmer indicates).
  2. Set your choke to OFF.
  3. Squeeze or position the throttle as if you’re running the strimmer at full speed.
  4. Pull on the starter cord several times rapidly.

At this point, you may hear the engine sputter or see black smoke leave the exhaust.  This is the flooded fuel being cleared.  Eventually the engine will run.

Do not ease up on the throttle until the engine feels like it’s running normally.  Once it does, slowly ease the throttle down to more of an idle before securing.

By following this procedure, you’re making the engine draw small amounts of fuel from both the carburetor and the flooded combustion chamber, clearing it out until the fuel/air ratio is rebalanced and the spark is able to ignite the corrected mixture.

7.  When to Take Your Strimmer in to a Service Center

There are times when easy fixes don’t work and it’s time to admit it’s also time to take your equipment in for a technician to inspect, repair, and possibly replace part of or your entire strimmer all together.

One time is if the carburetor needs more complicated repairs than a simple repair/rebuild kit provides.  It may be so bad the entire carburetor needs replacing.

Another time is if your pull cord starter needs work.  At that point, no amount of quick fixes regarding flooding will help because until the starter is addressed, there won’t be any starting.

Lastly, if the flooding has been so severe that your engine has experience a hydrolock (or so much fluid build-up that the engine has essentially seized).  This can lead to what would be considered a catastrophic failure and may require an engine rebuild or replacement.


A strimmer engine that keeps flooding sounds like a terrible thing.  After all, nothing with the word flooding paired with it really sounds great.  However, in the case of a flooding strimmer, the good news is there’s often a quick fix to what is often a mild issue.

That being said, you should still acknowledge the fact that an engine that continues to flood may be an indication there might be a more complex problem which needs to be dealt with in the near future.

In other words, yes there is a way to clear a flooded engine and get back to work.  Addressing why the engine is being flooded is just as important.