Unfortunately, the grass doesn’t stop growing just because your mower isn’t working. It can be very frustrating when your mower won’t start. Resolving your problem is a must before your yard turns into an unmanageable jungle.
A SCAG lawn mower won’t start when it can’t get the air, fuel or spark it requires. This can be due to a plugged air filter, old fuel, plugged fuel filter, clogged fuel lines, dirty carburetor, failed fuel pump, bad battery, faulty ignition switch, bad safety switch, or dirty spark plugs.
Continue reading for additional items that can prevent your SCAG mower from starting. As always, consult your operator’s manual to ensure you are following all safety procedures to prevent injury while working on your lawn mower.
This guide addresses gas-powered lawn mowers. If you happen to have a diesel-powered SCAG mower, refer to this guide for diesel lawn mower starting issues.
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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, knowledge or are not in the condition to perform the repair safely.
15 Reasons a SCAG Lawn Mower Will Not Start
Fuel Tank is Empty on Your SCAG Lawn Mower
Even though you know SCAG mowers can’t run without fuel, it’s easy to forget to check the simple things when you’re frustrated. You may have forgotten to refill your fuel tank or you may have developed a fuel leak resulting in the tank emptying quicker than usual.
Repair: Check and repair any fuel leaks. Add fresh fuel to your gas tank.
Wrong Type of Fuel or Old Fuel in a SCAG Lawn Mower
Type of Gas to Use in a SCAG Lawn Mower
A SCAG gas-powered lawn mower requires an unleaded gasoline with an octane-rating of 87 or higher and an ethanol content of 10 percent or less. Do not use gas with a higher ethanol content as ethanol can cause damage to the engine. Read my guide on the type of gas to use in your SCAG mower.
Use Fresh Fuel in a SCAG Mower
Gas-powered SCAG mower:
Old gas can keep your SCAG mower from starting. This is because gas develops a sticky substance that can clog the fuel system. The moisture ethanol attracts will also cause corrosion of the fuel components making them fail to work.
Because fuel can begin breaking down and becoming less effective as quickly as 30 days after you purchase it, it’s best to consume the gas within this time frame. If you buy more fuel than you can consume right away, use a fuel additive to stabilize it.
Repair: Drain and flush the fuel tank using a fuel siphon. Add fresh fuel with a fuel additive to stabilize, clean and reduce moisture in the fuel system like Sea Foam Motor Treatment. Read more about why I choose to use Sea Foam here.
Fuel Cap Won’t Vent on a SCAG Lawn Mower
There is a vent in the fuel cap that allows air to pass through the cap. Without a vent, the fuel tank will act like a vacuum and keep fuel from leaving the fuel tank. When the fuel tank vent gets plugged, your SCAG mower won’t get the fuel it requires to start and run.
Run your mower with and without the fuel cap to find out whether or not your mower will start without the fuel cap and whether it will die with the fuel cap on after running a while. If your mower starts without the cap and dies with it in place, there’s a good chance your gas cap is plugged.
Repair: You can try to clean the cap to remove the clog. If you are unable to get the fuel cap to vent, you must replace the fuel cap.
Bad Spark Plug or Loose Connection on a SCAG Lawn Mower
The spark plug can become dirty and covered by carbon causing it to misfire and not start. Clean the spark plug off with a wire brush unless it is really dark in color. If it’s this bad, it’s best to replace the spark plug.
You’ll also want to replace the spark plug that has a cracked porcelain insulator or burnt electrode. The spark plug is a maintenance item that should be replaced at least once a year.
Repair: Remove your spark plug and inspect it for signs of carbon buildup or cracked porcelain insulator. Replace with a new spark plug(s) when you find these items. Make sure they are correctly gapped according to the engine manufacturer. Securely attach the spark plug wires.
Plugged Air Filter in a SCAG Lawn Mower
The air filter is the first line of defense protecting your lawn mower’s engine from foreign particles entering the engine. Dirt and debris in the engine can cause significant harm including damage to the seals and scoring to the cylinder.
The air filter is an inexpensive part to protect the engine . It’s important to check and clean the filter several times throughout the mowing season to ensure it stays clean. If you avoid replacing and cleaning your air filter, it can become so plugged, air won’t be able to pass through the filter to the engine.
It is good practice to start each mowing season with a new air filter and then regularly clean it. Not taking time to clean it may cause extensive engine damage and a large repair bill.
Repair: Check the air filter for dirt and debris buildup. Follow these steps for cleaning a paper air filter:
- Carefully remove the air filter from the housing. Be careful. You don’t want to knock any dirt into the air intake.
- Remove any dirt remaining in the housing with a dry clean cloth.
- Tap your filter against a solid surface. What you are doing is knocking as much dirt loose from the filter as possible so it falls out of the filter. Don’t use compressed air to clean the filter as it can damage the filter.
- Check to see if your filter can be reused. Do this by holding the filter up to a light source. If you can see light shine through the paper, it is okay to reuse it. If you don’t, it’s time to buy a new air filter. (Never run your SCAG without an air filter even if it is for a short period of time).
- Install the air filter into the housing and reattach the filter housing cover.
Plugged Fuel Filter on a SCAG Lawn Mower
The fuel filter strains fuel coming out of the fuel tank so dirt and other contaminates don’t enter the fuel system. The filter can become clogged if it isn’t changed annually or it is filtering very dirty fuel. A clogged filter won’t allow fuel to pass through the filter so your SCAG won’t start.
Repair: Install a new fuel filter with the arrow on the side of the filter pointing in the direction of your mower’s fuel flow.
Clogged Fuel Line on a SCAG Lawn Mower
Dirt and sticky deposits left behind from old fuel can become lodged in your mower’s fuel line. Your SCAG won’t start when the fuel line is plugged restricting fuel flow.
Check for a blockage in your fuel line by stopping your fuel flow, removing the end of hose from a section of fuel line furthest from the fuel tank. Place the line in a container and start the fuel flow. If you are not getting sufficient flow, you will need to remove the line and remove the restriction.
Repair: To clean the clog, stop the fuel flow. Remove the fuel line, spray carburetor cleaner into the tube and use compressed air to blow air through the tube until the line is free of debris and gummy residue. Repeat as necessary. If you are unable to clear the clog you will need to replace the fuel line.
Bad Fuel Pump on a SCAG Lawn Mower
Most SCAG mowers use a vacuum fuel pump to move fuel from the fuel tank to the carburetor. When the pump is no longer able to build pressure using the vacuum in the crankcase, it must be replaced.
If you find find the fuel pump cracked or leaking fuel, go ahead and replace it. If not, perform the following test to see if it is functioning correctly:
- Make sure you are getting fuel to the inlet port of the fuel pump. If you are not, check for a restriction in the fuel line or fuel filter.
- Once you confirm you are getting fuel to the pump, shut off your fuel supply, remove the fuel line from the carburetor and place it in a container to collect fuel.
- Turn on your fuel supply and start your SCAG mower.
- Watch for a steady or pulsating supply of fuel coming out of the fuel line and into the container.
Repair: If you aren’t getting sufficient fuel flow, your fuel pump may be damaged and will need to be replaced.
Clogged & Dirty Carburetor on a SCAG Lawn Mower
Your carburetor can become dirty from running old fuel through your lawn mower. Fuel can leave deposits in the carburetor that can build up so your carburetor is no longer able to function as it is designed to.
A carburetor’s main job is to regulate the amount of fuel is mixed with air to form a combustion in your engine’s cylinder.
Repair: 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 the carburetor including the float bowl and needle.
You can find steps for cleaning your carburetor here. If the carburetor is too dirty to clean adequately, you should replace it. If you don’t want to tackle the cleaning task, your local SCAG dealership or small engine repair shop can do this for you.
Bad Battery, Loose Cables or Corroded Terminals on a SCAG Lawn Mower
A SCAG mower will not start with a bad battery, loose cables or corroded terminals. Confirm your battery terminals are not corroded and are attached securely to the battery.
Repair: Clean corroded terminals in a baking soda solution containing 2 cups of water and 3 rounded tablespoons of baking soda. Use a wire brush to scrub the terminals clean.
Test your battery with a multimeter. You will want a reading at about 12.7 volts. Place on a charger to charge your battery if your reading is less than this. Read more about the steps and items needed to charge your battery here. If your battery does not hold a charge, you will need to replace it with a new battery.
Bad Safety Switch on a SCAG Lawn Mower
Your SCAG lawn mower may use several safety switches designed to keep the operator safe. The manufacturer installs safety switches to prevent the mower deck to run without the operator present.
It also has a safety switch involved to not start when your parking break isn’t engaged. If these safety switches fail, your mower may not start.
Repair: Test the switch using a multimeter or you can temporarily bypass the safety switch to identify a bad switch.
Do not operate a mower without the safety switch. Never run a mower when a safety switch is bypassed. You never know when you will encounter a situation where the safety switch can save you from serious injury.
Bad Ignition Switch on a SCAG Lawn Mower
You insert the key into your ignition switch and turn it only to find your SCAG mower doesn’t start or even turn over. The ignition switch could be the problem.
Repair: You can use a multimeter to test the ignition switch. Replace the switch if bad.
Bad Ignition Coil on a SCAG Lawn Mower
The ignition coil provides voltage to the spark plug so it can fire and start the engine. The engine will not start if the spark plug isn’t able to fire.
Repair: After you verified your spark plug is in good condition, check the continuity of your ignition coil using a multimeter. Replace the ignition coil if you find a break in the continuity.
Faulty Charging System on a SCAG Lawn Mower
A charging system that is no longer able to keep your SCAG mower running can cause it to die while you are mowing. It can also cause your battery to be drained preventing it from starting the next time you go to use your mower. A bad stator or alternator can be the problem. I show steps on how to test your charging system here using an ohm meter.
Repair: When you find your SCAG starting problem is due to the charging system, take your lawn mower to your local SCAG dealer for further troubleshooting and repair.
If you don’t have experience with charging systems, you will most likely just throwing different parts at your mower hoping to fix it.
The cost of all of these parts can get pretty expensive if you don’t guess right the first time. Most lawn mower centers do not allow you to return electrical parts so you will be stuck with the part whether it is the problem or not.
Incorrect Operating Procedure on a SCAG Lawn Mower
SCAG has different safety features that require the operator to follow certain steps to start the mower safely. For example, the operator must be in the seat, the parking brake must be set, and the levers must be in the neutral position. The choke setting may not be set correctly preventing the mower from starting as well.
Repair: Refer to your SCAG mower operator’s manual to ensure you are starting your lawn mower correctly.