When your string trimmer won’t stay running, it’s best to troubleshoot your string trimmer before you replace it with a new one. It may be a bad maintenance item or a simple fix.
A Honda string trimmer starts then dies when it isn’t getting sufficient fuel, air, and spark.
This may be due to a dirty carburetor, clogged fuel filter, clogged fuel line, bad spark plug, faulty ignition coil, plugged air filter or plugged spark arrestor.
Keep reading for more items that may cause your starting problem. Before repairing your string trimmer, disconnect the spark plug boot and wait for all moving parts to stop.
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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.
10 Reasons Your Honda String Trimmer Starts Then Dies
1. Incorrect Choke Setting on a Honda String Trimmer
If your Honda string trimmer starts fine and then dies right after, check to make sure you have the choke lever set in the right position.
The choke is used to restrict air to allow more fuel to be pulled into the cylinder to start a cold engine. Once the engine warms, the choke must be adjusted to the open position to allow sufficient air to keep the engine running.
When the choke isn’t adjusted after the engine warms up, it will begin to sputter and die because it isn’t getting the fuel-to-air ratio required to keep it running.
SOLUTION: Check the choke lever to make sure it is placed in the off position once the engine is warm.
2. Plugged Air Filter in a Honda String Trimmer
Just like your Honda engine can die from a lack of air when the choke is left on, it can stall and die when clean air isn’t able to flow past a plugged air filter.
Your Honda string trimmer requires an air filter to prevent dirt and debris from getting sucked into the engine causing wear. It must be kept in good condition to keep dirt out while allowing air to pass through it.
I recommend replacing the air filter at the beginning of every lawn care season. Then check and clean the filter several times throughout the season.
Never run your string trimmer without an air filter, even if it’s just for a short period so you can finish your task. Doing so can compromise the engine.
SOLUTION: Clean the air filter. Purchase a new air filter if your filter is extremely dirty or damaged.
Clean a Honda FOAM string trimmer air filter:
- Remove the air filter cover and air filter.
- Clean the foam air filter using water and mild detergent.
- Rinse the filter until the water runs clear and allow it to air dry.
- Once dry, lightly saturate the filter with filter oil. Squeeze excess oil from the filter. (Do not oil pre-filters)
- Reinstall the filter.
- Reattach the air filter cover.
Consult your operator’s manual for instructions when cleaning other types of air filters.
3. Old or Bad Fuel in a Honda String Trimmer
Running old fuel through your Honda string trimmer can cause it to stall and run sluggishly. Most gasoline contains ethanol, a corn-based fuel that is added to make fuel more environmentally friendly.
While better for the environment, it is not good for the small engine used on your Honda. The gas and ethanol mixture can begin to break down as soon as 30 days after purchase.
Ethanol and the water it attracts are corrosive to the trimmer. It leaves behind a varnish that reduces the amount of fuel getting to the engine.
A fuel without ethanol is always best, but it is the more expensive fuel choice.
Tips for selecting gas for 4-cycle Honda string trimmers:
- 4-cycle engines require straight gas. Do not mix with oil.
- Use a gas with a minimum 87-octane rating.
- The gas must contain no more than 10% ethanol (E10). Avoid E15 and E85 fuels as these contain up to 15% and 85% ethanol respectively.
- Consume gas within 30 days of purchase.
- Add a fuel stabilizer to keep fuel stable a little longer.
Read more about choosing and caring for the right gas in this article about gas and oil for Honda string trimmers.
SOLUTION: Drain old fuel from the string trimmer. Fill with fresh fuel with a fuel additive like Sea Foam Motor Treatment mixed in to make the fuel stable, reduce moisture, and clean the fuel system.
Start the trimmer and allow it to run for 5-10 minutes to allow all of the fuel to work its way through the fuel system.
4. Plugged Fuel Filter in a Honda String Trimmer
The fuel filter helps keep the fuel system clean and free of dirt and debris that may get into the fuel tank. You will find the fuel filter on your Honda string trimmer attached to the fuel line inside the fuel tank.
A fuel filter should be replaced annually and possibly more often if you happen to be running dirty fuel.
When it isn’t changed, the filter can become so plugged that a sufficient amount of fuel isn’t able to pass through the filter causing your Honda trimmer to run sluggishly or quit running.
SOLUTION: Replace the fuel filter. If the fuel is dirty, replace it with fresh fuel.
Replace a Honda fuel filter:
- Wipe around the fuel cap to remove dirt, and then remove it.
- Empty the fuel tank into a clean fuel container.
- Set the trimmer on a flat surface.
- Pull the fuel filter out of the tank using a clean bent wire to hook the fuel line. Needle nose pliers may also work.
- Securely holding the fuel line, securely grab the filter and pull it out of the fuel line.
- Install a new fuel filter at the end of the fuel line.
- Place the filter back inside the fuel tank.
- Fill with fresh gas
- Place the fuel cap onto the fuel tank.
5. Clogged Fuel Lines on a Honda String Trimmer
Old fuel can leave behind deposits that stick inside the fuel lines. This narrows the passageway and the amount of fuel that flows through the line.
SOLUTION: When this happens, remove the fuel line and install a new fuel line of the same diameter and width. You will need to replace the fuel line if you find it is dry, cracked, or kinked.
6. Plugged Fuel Tank Vent on a Honda String Trimmer
The Honda fuel tank requires a vent to allow air to pass through it. When this vent is plugged a vacuum is created in the fuel tank. It doesn’t allow fuel to flow out of the tank which causes the trimmer to stall and die.
If you are not getting fuel to the carburetor, you are running a good filter, and you don’t have any clogs in the fuel lines, you may have a clogged fuel tank vent.
SOLUTION: You can check the pressure of the tank with a pressure gauge to make sure there isn’t a vacuum buildup. However, most people don’t have a fuel line pressure gauge on hand.
Follow the instructions below to determine whether the fuel tank is venting properly.
Perform this simple test to help identify a bad fuel tank vent:
- Loosen the fuel cap to allow air into the tank and start the trimmer. Don’t allow gas to spill out of the fuel tank.
- Start the engine and allow it to run. If it runs fine and doesn’t begin to sputter or stall, you may have a vent problem.
- Try to replicate the issue to further confirm the vent is the problem.
- Tighten the fuel cap and run the string trimmer. If it begins to run sluggish or shuts down and doesn’t start again until you loosen the fuel cap, replace the fuel tank vent.
On most Honda trimmers, the fuel tank is built into the fuel cap.
7. Dirty Carburetor on a Honda String Trimmer
The carburetor mixes the correct proportion of air and fuel required for your Honda string trimmer to run. The passageways can become clogged and the small components can fail to function correctly.
This can cause an insufficient amount of fuel mixed with air resulting in a rough running string trimmer that may just quit.
SOLUTION: You may be able to clean your carburetor to get it working again. You may end up having to rebuild it (if rebuild kits are available for your Honda carburetor) or replace the carburetor if cleaning doesn’t help.
Before replacing a carburetor, I recommend comparing the cost of the carburetor and labor expense to the cost of a new Honda string trimmer.
Depending on the model, cost, and age of your string trimmer, you may be better off purchasing a new trimmer.
8. Dirty Spark Plug on a Honda String Trimmer
The spark plug will become dirty over time with a buildup of carbon. This can cause the plug to misfire having intermittent starting problems.
Other items to look for are cracked porcelain or worn electrodes; a loose spark plug wire; and an incorrect spark plug gap. These items can also cause a running issue with your Honda.
SOLUTION: You can attempt to clean a dirty spark plug with a wire brush and reuse it. I prefer to replace it especially if it’s the reason your trimmer is dying.
It is an inexpensive part and one of the primary items responsible keep your string trimmer running at its best.
Make sure your spark plug is gapped to the manufacturer’s specification and the spark plug wire (boot) is securely attached.
9. Bad Ignition Coil on a Honda String Trimmer
The winding on the ignition coil can separate and short out. When this happens, the spark plug won’t get the voltage required to create a spark. This will cause your Honda to die after it’s been running.
SOLUTION: Identify a bad ignition coil using an ohmmeter to check for a break in continuity. Replace the ignition coil if you find a break.
10. Plugged Spark Arrestor on a Honda String Trimmer
There is a small metal screen that keeps hot exhaust material from shooting out of the string trimmer and causing injury or starting a fire. This small screen will become plugged with a carbon buildup that will affect how the engine runs.
SOLUTION: Disconnect the spark plug wire. Carefully remove the spark arrestor screen and inspect it for damage.
If it is in overall good condition, clean it with a wire brush and reinstall it. However, if it is damaged or has a hole in it, you must replace it with a new spark arrestor screen.
Contact your local Honda service center if you are having trouble locating the spark arrestor screen or if you are continuing to experience problems with your Honda string trimmer.