A chainsaw is a good tool to have on hand to clean up after a storm or to cut a little wood for heating. For most homeowners, it’s not an item you use regularly so it is frustrating when you go to use it and the engine won’t start.
A SENIX chainsaw won’t start when it doesn’t have sufficient air, fuel, or spark to form combustion.
A bad on/off switch, old fuel, plugged fuel filter, clogged fuel line, dirty carburetor, plugged air filter, plugged spark arrestor, bad spark plug, or faulty ignition coil can keep a chainsaw from starting.
Keep reading for additional reasons your chainsaw won’t start. Remove the spark plug wire before beginning any repairs.
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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.
This is Why a SENIX Chainsaw Won’t Start
Bad On/Off Switch
The switch on your chainsaw must be placed in the on position to start. If you find that is in the off position, flip it to on.
A faulty switch or bad ground wire can be the reason a chainsaw won’t start.
SOLUTION: Use a multimeter to test the switch. Replace a bad switch. Repair or replace a bad ground.
Old Gas or Water in the Gas
Most gasoline today has an alternative fuel added to it to make it a little better for the environment. This fuel, made of corn or another high-starch plant, is known as ethanol.
While ethanol is usually okay to run in most vehicles, it is not good for small engines like the one in your chainsaw.
Ethanol attracts moisture from the air to the fuel system. The ethanol and water mixture will leave behind a sticky varnish that can gum up the fuel system and cause clogs and failures.
Because gasoline begins to lose volatility and becomes less effective as soon as 30 days after purchase, it’s important to use the gas within this period.
If you are unable to consume it this quickly, add a fuel additive to stabilize the gas so it lasts a little longer.
SENIX 4-cycle chainsaws require straight gas. DO NOT MIX WITH OIL. Use a gas that has a minimum 87 octane rating and a maximum 10% ethanol content.
Avoid gas with high levels of ethanol content like those sold as E15 and E85. These fuels have up to 15% and 85% ethanol content respectively.
SOLUTION: Drain any old gas remaining in your chainsaw. Fill with a fresh gas with a fuel additive like Sea Foam Motor Treatment or STA-BIL mixed in to help reduce moisture, clean the fuel system, and keep gas stable.
Dirty Air Filter
The air filter is an important component used to protect the engine. A filter keeps dust and sawdust from passing through the filter and into the carburetor throat preventing wear on the engine.
When the air filter isn’t regularly cleaned or replaced, the buildup of dirt can be so significant that good airflow isn’t able to pass through it. A plugged air filter will prevent your chainsaw from starting.
It’s good practice to replace your air filter annually and clean it several times throughout the season if you’re the average homeowner. If you use your chainsaw a lot, you’ll have to clean and replace the filter more often.
Take time to inspect your air filter to prevent overheating the engine and causing damage. I know this is one more step, but it takes less than a minute to check the condition of the filter and can prevent engine damage. If the filter is extremely dirty or damaged, it must be replaced.
Never run a chainsaw without an air filter. You may get tempted to run your chainsaw just a little longer to finish your task until you get a new air filter replacement, but doing so puts the engine at risk of damage.
Steps to clean a chainsaw filter:
- Remove the air filter cover.
- Remove the air filter.
- Wipe out any dirt from the air filter housing.
- Tap the filter against a solid surface to get the remove as much dust as possible.
- If needed, wash it with water and allow the filter to completely dry.
- Reinstall the clean filter. Purchase and install a new air filter if the old filter is extremely dirty, damaged, or is unable to properly seal leaving a gap where dirt can bypass the filter.
- Reattach the air filter cover.
Fouled or Damaged Spark Plug
The spark plug provides the spark required to start and keep the chainsaw running. The spark plug is a wear item that should be changed annually for the casual user.
If you use your chainsaw regularly, you may need to change it as often as monthly.
Inspect the spark plug and clean it with a wire brush in between replacements. A dirty spark plug can cause the spark plug to misfire causing running issues.
Replace a spark plug if you find it is very dark in color, has a burnt electrode, or broken porcelain. Make sure the spark plug is gapped to SENIX’s specification and the spark plug wire is securely attached.
A loose spark plug wire or improperly gapped plug can cause a starting problem.
Faulty Ignition Coil
If the spark plug is in good condition, but you still aren’t getting spark, check the ignition coil. 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 chainsaw to fail to start.
Identify a bad ignition coil using an ohmmeter to check for a break in continuity. Replace the ignition coil if you find a break.
Clogged Fuel Filter
Like the air filter is used to keep dirt out of the air intake to prevent wear on the engine, the fuel filter is used to keep dirt out of the fuel system.
The fuel filter on a chainsaw is located in the fuel tank. It is attached to the end of the fuel line to strain fuel before it enters the line.
When the filter isn’t changed regularly or when dirty fuel has been used, it can become plugged restricting the amount of fuel that is able to pass through the filter.
SOLUTION: When your isn’t able to get a sufficient supply of fuel, it will fail to start or run sluggishly. Replace the fuel filter annually and more often if you use the chainsaw regularly.
Replace a chainsaw fuel filter:
- Wipe around the fuel cap to keep any dirt from falling into the fuel tank when removing the fuel cap.
- Remove the fuel cap.
- Use a clean bent wire to hook the fuel line and pull the fuel filter out of the tank.
- With one hand securely holding the fuel line and ring clip, pull the filter out of the fuel line with the other hand.
- Install a new fuel filter by inserting the male end into the fuel line making sure the ring clip is securely holding the fuel line to the filter.
- Place the filter in the fuel tank and reinstall the fuel cap.
Bad Primer Bulb
A cracked primer bulb that won’t fill up with fuel won’t function correctly to get fuel to the carburetor.
SOLUTION: Replace with a new primer bulb.
Clogged or Punctured Fuel Line
Letting fuel sit in your chainsaw can cause buildup in the fuel line restricting fuel flow. You can try to remove the blockage and clean the line using a carburetor cleaner.
SOLUTION: Remove the clogged line, spray carburetor cleaner into the line to loosen up the clog, and blow compressed air through the line to remove the clog.
If you are unable to successfully remove the blockage or you find the fuel line is damaged, punctured, or cracked, it’s best to replace it with a new fuel line.
The carburetor regulates the amount of fuel that is mixed with air to create combustion in the cylinder. Old fuel will gum up and clog the carburetor so it no longer functions as designed. This can keep your SENIX from starting.
SOLUTION: If you are a little mechanical you should be able to handle cleaning your carburetor. Clean the carburetor by taking it apart and using carburetor cleaner to clean it.
If the carburetor does not function after being cleaned, you may need to rebuild it or replace it with a new carburetor.
Bad Recoil Starter
Your chainsaw uses a recoil to start the engine. A bad pulley; loose or missing spring; or broken clips can keep your recoil from working.
SOLUTION: You can attempt to replace the spring and restring the recoil. If it does not work because other components in your recoil are damaged, such as the clips or the pulley, you are better off just replacing the recoil assembly.
Plugged Spark Arrestor
The spark arrestor is a small screen that can get plugged with soot. A plugged spark arrestor will prevent airflow causing your chainsaw not to start.
SOLUTION: Remove the spark arrestor and clean it with a wire brush. Replace the mesh spark arrestor screen when you are not able to clean it sufficiently or if it is damaged.
Never run your SENIX without this screen or with a screen that has a hole in it.
The engine can become flooded when the choke is in the closed position and the starter rope was pulled many times.
It can also happen with the switch off and the starter rope being pulled multiple times or when the primer bulb is pushed too many times.
How to Fix a Flooded Engine on a SENIX Chainsaw
- Push the choke knob all the way in so it’s in the RUN position.
- Remove and dry the spark plug.
- Place the chainsaw on its side. The spark plug hole should be pointed away from you.
- Pull the starter rope 6 to 8 times to drain fuel from the combustion chamber.
- Reinstall the clean spark plug.
- Start the chainsaw.
Where to get Repair Support for Your SENIX Chainsaw
Unlike some well-known brands, it’s more difficult to find a local service center that repairs SENIX chainsaws.
You can call SENIX support at 1-800-261-3981 on Monday-Friday from 9AM – 5PM. You can also contact support online, but it will take a day or two to get a response.
Where to Find Parts for Your SENIX Chainsaw
I have found sourcing parts for a SENIX Chainsaw difficult as well. The operator’s manual provides a limited list of parts with part numbers for the saw. However, it’s hard to find a place to purchase these parts.
SENIX offers some parts on its website, but the parts offered are extremely limited. You may be able to find a bar and chain, but not much more.