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10 Reasons a SENIX Mower Won’t Start: Fix SENIX Starting Problem

When you can’t get your mower to start, you need to either fix it yourself or borrow a mower while you wait for a repair shop to fix it. There are many items that may cause a starting problem you can easily fix yourself.

A SENIX lawn mower won’t start when the engine isn’t getting sufficient air, fuel, and spark.

This may be caused by old fuel, a clogged fuel line, a dirty carburetor, a plugged air filter, a bad fuel cap, a bad spark plug, a faulty ignition coil, or a bad recoil.

Before performing any repairs on a SENIX Mower, follow all safety procedures outlined in your operator’s manual. This includes removing the spark plug wire.

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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.

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Reasons Your SENIX Lawn Mower Won’t Start

1. Empty Gas Tank

The fuel tank on a SENIX mower is small. It’s easy to run out of gas if you forgot to check the fuel level before you started mowing.

You may have developed a fuel leak causing you to run out of fuel faster than normal or you may have just simply forgotten the last time you filled the fuel tank.

Don’t forget to check the fuel tank before moving on to checking other items for your starting problem. Fill the tank if you find it is low on gas.

2. Bad or Old Fuel

It’s not good to let fuel sit in your SENIX for long periods and not consume it. Gas can begin to break down and lose its combustible properties soon after purchase.

Much of today’s fuel contains ethanol, an alternative plant-based fuel, to make fuel more environmentally friendly. While fuels with ethanol are okay to run in most vehicles, it’s not good for the small engine on a SENIX.

Ethanol attracts moisture to the fuel system. This water and ethanol mixture will leave behind varnish and gummy deposits when left sitting in your mower for long periods. This will cause fuel restrictions and fuel component failure.

Because of the negative effects ethanol has on a SENIX mower, it’s important to keep these things in mind when purchasing, storing, or consuming fuel:

  • Purchase fresh fuel with a minimum 87 octane rating.
  • Never use gas with more than a 10% ethanol content. Ethanol-free fuel is best.
  • Consume fuel within 30 days.
  • Use a fuel stabilizer if you are unable to consume it within 30 days to make it last a little longer without breaking down. (Fuel stabilizer must be added to fresh fuel. It will not reverse the effects of old fuel).
  • Store fuel in an approved fuel container away from moisture or combustible products.

If you find old fuel in your SENIX mower, drain the gas. Mix fresh gas with a fuel additive to help clean the fuel system, reduce moisture, and stabilize the gas.

I like a product called Sea Foam Motor Treatment. I use this product in every tank of gas to help reduce the issues that can result from using fuel with ethanol.

Read more about the advantages of using a fuel additive like Sea Foam here.

3. Blocked Fuel Line

The gummy deposits or dirt left behind by old fuel can clog the fuel system including the fuel line. Check for clogs in the fuel line that could be restricting fuel to the engine.

To do this, shut off the fuel supply using the fuel shut-off valve (if your mower uses one) or clamp the fuel line to stop fuel flow. Remove the end of the fuel line attached to the carburetor with the fuel shut off.

Place the line in a container. The container must be placed lower than the fuel tank so fuel can use gravity to flow. This is because fuel can’t run uphill without the assistance of a pump.

With the fuel line in the container, turn on the fuel supply and watch it flow into the container. If you are getting a good flow of fuel, the problem is not in the fuel line. Stop the fuel flow and reattach the line.

If you aren’t getting good flow, with the fuel flow off, remove the fuel line from the lawn mower. If you don’t have a fuel shut-off valve, your only option may be to drain the fuel tank to stop the flow before removing the line.

Once the line is removed from the mower, spray carburetor cleaner into the line to loosen the clog. Blow compressed air into it to remove the clog. Repeat using carburetor cleaner and compressed air until the line is free of any clogs.

Reinstall the fuel line once you have removed the restriction. Purchase a new fuel line if you can’t remove the clog or if the line is damaged or cracking due to age.

If you find the problem wasn’t in the fuel line, proceed with checking the fuel strainer.

4. Plugged Fuel Strainer

If you find you have a fuel restriction before the carburetor and the fuel line isn’t clogged, it’s time to check to see if your mower has a fuel strainer. This is a small part attached at the bottom of the fuel tank to strain fuel before it enters the fuel line.

This part is often installed to keep dirt and other debris from getting into the fuel system and causing engine wear.

With the fuel tank drained, remove the fuel strainer and inspect for clogging. Clean the screen to remove dirt or replace it with a new one if needed.

5. Dirty Carburetor

The carburetor’s function is to regulate the amount of gas mixed with air to form combustion in the cylinder.

When the carburetor is dirty and gums up from old fuel, components in the carburetor no longer function properly. The carburetor may not allow the gas required to start your SENIX mower.

If you have verified you are getting fuel to the carburetor, remove the air filter and spray carburetor cleaner into the air intake. Start your mower.

If the engine starts, runs, and then shuts down once the carburetor cleaner is burned, take the carburetor apart to clean it.

6. Bad Gas Cap

The fuel tank on your SENIX must vent to allow air into the tank as fuel is consumed. Without a vent, a vacuum forms keeping gas from flowing out of the tank to the carburetor. Your mower won’t start when it isn’t able to get fuel.

A SENIX fuel tank vents through the fuel cap. A bad cap or one that has a clogged vent will need to be replaced.

To determine whether your cap is the cause of your starting problem, loosen or remove your cap to allow air inside the tank and then attempt to start the mower.

If it starts, but stops running again after you place the cap back on the mower and allow it to run for a while, you may have a problem with the cap. You should replace a bad fuel cap.

7. Clogged Air Filter

A plugged air filter can restrict airflow to the mower and not allow the engine to get the air it needs to form combustion. It is best practice to replace your air filter annually.

You must also check and clean the filter regularly throughout the mowing season.

Clean a SENIX PAPER air filter:

  • Remove the air filter cover.
  • Remove the air filter.
  • Remove loose dirt in the air filter housing and from the air filter cover using a clean dry cloth. Be careful and don’t allow dirt to fall into the air intake.
  • Tap the air filter element against a solid surface to loosen dirt so it falls out of the filter.
  • Hold the filter up to a light source. If you can see good light through the paper, go ahead and continue to use the filter. If you can’t see good light or the filter is damaged, the filter needs to be replaced with a new one.
  • Install the new or clean air filter.
  • Reattach the air filter cover.

Clean a SENIX FOAM air filter:

  • Remove the air filter cover.
  • Remove the air filter.
  • Remove loose dirt in the air filter housing and from the air filter cover using a clean dry cloth. Be careful and don’t allow dirt to fall into the air intake.
  • Inspect the air filter for damage. If it is very dark in color, brittle, or has tears in it, it’s time to replace it with a new one. If it is in good condition, continue cleaning the filter.
  • Wash the foam filter in water and mild detergent to remove oil and dirt.
  • Rinse the filter until it runs clear. Squeeze the filter to remove water. Don’t wring the filter as this can tear it.
  • Allow the filter to dry.
  • Apply clean engine oil to the filter so it is completely covered. Squeeze excess oil from the filter. (NEVER APPLY OIL to a foam pre-filter. A pre-filter is a filter that wraps around a paper filter element. This can damage the paper filter).
  • Install the filter.
  • Reattach the air filter cover.

8. Bad or Improperly Gapped Spark Plug

A spark plug can be faulty when the tip is dirty, the porcelain is cracked or the electrode is burnt. This will cause your mower not to start.

You can clean the spark plug to remove the deposits using a wire brush. If your spark plug tip is very dark in color or damaged, you must replace your spark plug.

Your spark plug needs to be properly gapped following the manufacturer’s specifications as found in the operator’s manual. Starting problems can be caused by a spark plug that is gapped incorrectly or the spark plug wires being loose.

9. Bad Ignition Coil

Before checking for a bad ignition coil, make sure your spark plug is in good condition. The ignition coil provides voltage to the spark plug so it can start the engine.

If the spark plug isn’t able to fire, the engine will not start. Check the continuity of the ignition coil using an ohmmeter. If you find a break in the continuity, replace the ignition coil.

10. Bad Recoil

The recoil on your mower may no longer be able to start your mower. A rope on the recoil can become unstrung or you may find you have a broken pulley, springs, or clips in your recoil that need to be repaired.

Sometimes, restringing the recoil is all you need. Other times you will have to replace broken parts in your recoil. Before doing this, price out a full recoil replacement.

Depending on the price difference, it may be better to replace the recoil assembly over tearing it down and replacing broken components.