Big Dog Zero Turn Mower Won’t Start for These 17 Reasons

If the air and fuel mixture that the spark plug is supposed to ignite doesn’t get started, the Big Dog zero-turn mower won’t start.

Possible causes include a faulty spark plug wire, a dirty carburetor, a weak battery, rust on the electrical components, faulty safety switches, outdated gas, or a clogged air filter.

Be careful while you try to diagnose and fix the starting issue with your Big Dog. Before making any repairs, turn off the engine, disconnect the spark plug wires, and let everything come to a complete stop.

The operator’s manual will provide further instructions for safety.

Before diagnosing, repairing, or operating, be sure you’ve read and understood all of the safety recommendations in the equipment’s operator’s manual.If you are unsure about how to proceed or if you lack the necessary expertise or experience, you should seek the assistance of a professional.

What You Should Do If Your Big Dog Mower Won’t Start

Your Big Dog Zero Turn’s Gas Tank Is Empty

Because of a fuel leak, a broken gas gauge, or simple forgetfulness, you may not remember that the gas tank is nearly empty.

ANSWER: Put some new gas in the tank.

• Check for fuel leaks and fix them if you find them.
• Verify that the gas gauge is functioning properly.
• Put in fuel with an octane rating of 87 or above and no more than 10% ethanol.

Using Old Gas in Your Big Dog Mower

After roughly 30 days, gas starts to degrade, break down, and become less effective.

Ethanol, an additive to most gasoline, is known to draw moisture into the fuel system. As a result, the fuel lines, filter, and carburetor become clogged with varnish and sticky residue.

How to prevent your Big Dog mower from being damaged by old fuel:

• Get new gas with at least an 87 octane rating and 10% ethanol content.
• Within 30 days, all gasoline must be used.
• Add a fuel stabilizer to gas to keep it from degrading as quickly. Learn more about these fuel-enhancing chemicals by reading this.
• Keep gas away from water and humidity.

The solution is to drain the tank of its old fuel and replace it with new fuel and an additive designed to cleanse the fuel system:

• Loose dirt and debris should be wiped away from the area around the fuel cap. Take off the top.
• If possible, use a fuel siphon pump to transfer the fuel to a safe storage container.
• Put some Sea Foam Motor Treatment, or whatever fuel additive you choose, into your new gas tank. This will help keep the gas more stable for longer by removing moisture and cleaning up the fuel system.
• Start the Big Dog and let it run to circulate the modified fuel mixture through the fuel system if you can.
• If it still won’t turn on, try the following. Once you’ve gotten the mower started, let it keep going for a bit.

Big Dog Mower with Leaky Gas Cap

As gasoline is used up, air must be able to enter the fuel tank through a vent. A vacuum occurs inside the tank when the vent is blocked, preventing fuel from escaping and reaching the carburetor.

Big Dog lawn mowers have a gasoline tank vent located in the gas cap.

If your mower has suddenly stopped working and won’t start again, check to see if there is a vacuum problem by using a pressure gauge, or if you don’t have one, follow these procedures:

• Loose dirt and debris should be wiped away from the area around the fuel cap.
• To let air into the gasoline tank, loosen the cap.
• Get your mower going, if you can.
  If that doesn’t work, tighten the fuel cap and keep looking for the source of the problem.
  If your mower starts, make sure the fuel cap is secure and let it keep running. You want to recreate the scenario in which your mower loses power and eventually stops working because of a vacuum leak.
• It’s possible that the cap is no longer venting if the mower started when you loosened the cap but stopped after you tightened it and let it run for a bit.

If your gas cap is no longer allowing gas to escape, you should get a new one.

Big Dog Mower’s Loose Connection or Faulty Spark Plug

Inadequate spark plug connections or worn-out spark plugs could also be to blame for your Big Dog’s inability to start. If there is oil or carbon on the tip of a spark plug, it will foul out and the engine will not start.

IF a spark plug is extremely filthy or broken, replace it. It’s possible that your engine model calls for two spark plugs:

• Take off the boot from the spark plug wire.
• Remove any dust or debris from around the spark plug by wiping it.
• To take out the plug, you’ll need a spark plug socket wrench. You’ll need either a 3/4″ or 5/8″ socket, depending on the make and type of your engine.
• Look at the plug’s tip to see if it’s darkened from carbon buildup, has damage, or has worn out. A new spark plug
• should be installed if these problems are discovered.
• If it is only slightly unclean and in good condition, you can clean it using a wire brush.
• Make sure the spark plug gap is set according to the vehicle’s manual.
• Replace the old one with a new one.
• Get the spark plug wire connected. If you need to make further repairs, you must first disconnect the wire(s).

When the spark plugs get filthy or start to impede my zero-turn performance, I prefer to replace them. It’s a low-cost part of maintenance that can cause big problems if it’s not in good shape.

The spark plug(s) needs to be changed every year.

Big Dog Mower with Clogged Air Filter

Your Big Dog’s engine can’t function without air. If your air filter gets too dirty, it will restrict the flow of air to the engine, causing it to overheat and die.

If your air filter is clogged, your engine will need to locate another source of air to keep going. The engine could overheat and be severely damaged if it draws air from the crankcase to cool down.

Maintenance tasks include changing the air filter once a year and cleaning it multiple times during the mowing season.

The ANSWER is to check for damage or extreme filth on the air filter and to replace it if necessary. If a filter is only somewhat filthy, you can clean it with the instructions below.

If you need clarification on the filter type and cleaning procedures for your model, see the manual that came with it.

Cleanse a Big Dog PAPER air filter:

• Take out the filter and throw it away.
  
• Clean the air filter housing and cover by wiping away any lingering dust or debris. Keep the air filter free of dust and debris.
  
• Check the condition of the paper filter. Lightly tapping the filter can cause the grime to slip out of the filter. When a filter is in good condition, light will pass through it. However, if the filter is extremely unclean, broken, or no longer effectively seals the air intake, a new one should be installed.
  
• Put in a fresh one or a clean one if you can.
  
• The air filter cover must be reattached.

A Big Dog Mower with a Clogged Fuel Filter

The fuel filter serves as a first line of defense against debris and dirt entering the engine via the fuel supply. Verify that the same amount of fuel is flowing out of the filter as is being pumped into it.

If it doesn’t, it’s probably plugged and you can’t start your Big Dog until you substitute it.

Follow these instructions to change the gasoline filter:

• Use the gasoline shut-off valve or a clamp to stop the fuel line from flowing.
• Remove the fuel filter from the fuel lines by sliding the ends apart with needle-nose pliers.
• A directional arrow on the filter could indicate which way it should be inserted into the fuel lines. The arrow’s direction of motion should be in sync with the fuel’s flow.
• Replace the old filter with the new one and fasten the gasoline lines to the filter using the clamps.

A Big Dog Mower’s Fuel Line Got Clogged

The fuel line on your Big Dog mower is susceptible to clogging from deposits of old fuel and debris.

The fuel line must be disconnected, carburetor cleaner sprayed inside, and compressed air blown through the tube until the line is clean and free of gummy residue. A new gasoline line is another option.

A Big Dog Mower with a Faulty Fuel Pump

For the carburetor to function, a fuel pump must be installed. A gasoline pump is required to transfer gas from the storage tank to the carburetor when the tank is located lower.

Like any other mechanical device, a gasoline pump can break down after some time has passed. Old fuel may have deteriorated the pump parts, which would explain the problem.

Check your vacuum fuel pump for cracks as a first step in diagnosing a faulty fuel pump.

Cracks in the fuel pump or fuel leaking outside of it indicate that the pump is no longer receiving fuel under pressure from the crankcase and delivering it to the carburetor.

How to Spot a Faulty Vacuum-Type Fuel Pump:

• Before inspecting the pump, make sure fuel is entering the inlet port. If not, maybe there’s a blockage in the gasoline line or fuel filter. After you have gotten fuel to the pump, you may continue.
• You can use the fuel shut-off valve or a clamp on the fuel line to stop the fuel from flowing.
• To gather fuel, disconnect the fuel line from the carburetor and set it aside.
• Turn on the grass cutter and keep an eye on the stream as it enters the collecting device.
• A regular or pulsating fuel flow should be visible.
• If the gasoline line is not producing a sufficient amount of fuel, the fuel pump should be replaced.

Your Big Dog mower won’t start or run if the gasoline pump isn’t working properly.

Big Dog Mower with Filthy and Clogged Carburetor

The carburetor controls the ratio of fuel to air for combustion, allowing the engine to turn over and start. Old ethanol-containing fuel can leave a sticky residue and crusty buildup in the carburetor.

If the carburetor is unable to control the flow of fuel and air into the engine, your Big Dog will either run poorly or refuse to start.

You can attempt cleaning the carburetor yourself if you’re mechanically inclined; otherwise, take it to a lawn mower repair shop. This article will show you how to clean the carburetor on your Big Dog.

If the carburetor looks like it’s in terrible shape, you may want to consider getting a new one.

A Big Dog with Loose or Corroded Cables, Wiring, and Terminals

If you notice that your wires are slack or that your battery terminals have corrosion, you should fix this immediately.

Trace the positive cable’s extension to the solenoid, and the solenoid’s extension to the starter. Mower starting issues might arise from loose cables or corrosion buildup.

Maintain a thorough inspection of your Big Dog’s wiring and parts.

Fix: check sure all wiring is firmly secured to the mower parts and tighten the wires. To get rid of corrosion, combine baking soda with water.

First disconnect the negative cable from the battery, then the positive.

Big Dog Mower with a Dead or Weak Battery

You can’t start your Big Dog lawn mower without a fully charged battery. If the battery is low, it will need to be charged before it can be used. This is one among the many causes of a zero-turn’s inability to crank or turn over.

SOLUTION: Use a multimeter to check your battery. A voltage of 12.7 volts or such is required. If your battery level is below this, you should charge it. Find out why your Big Dog’s battery keeps dying, and how to charge it, right here.

You should get a new battery if the old one won’t retain a charge.

A Big Dog Mower with a Flawed Safety Switch

The operator presence control system of your lawn mower may consist of more than one safety switch. When the driver gets up from the seat, the engine automatically shuts off.

Your Big Dog might not turn over because of a broken switch that cannot tell if the driver is seated or not.

To determine if a safety switch is malfunctioning, it can be temporarily disabled. For your own protection, never run a mower without the safety switch in place.

Make sure that your machinery has functioning safety switches at all times. Switch out a broken one.

A Big Dog Mower with a Faulty Ignition Switch

You put the key in the ignition and turn it, but the car doesn’t start. You are unable to get your Big Dog mower going. It could be the ignition switch. A multimeter can be used to check the ignition switch.

REMEDY: If the switch is broken, substitute it.

A Big Dog Mower with a Faulty Ignition Coil

The spark plug needs voltage from the ignition coil in order to ignite and start the engine. If the spark plug doesn’t ignite, the engine won’t turn over.

After making sure your spark plug is fine, check the ignition coil’s continuity with an ohm meter. If you notice a break in continuity, you should replace the ignition coil.

Big Dog Mower with Faulty Starter Solenoid

A faulty starter solenoid is usually to blame when your Big Dog mower clicks but won’t start.

The electromagnetic “on/off” switch of a lawnmower solenoid activates the starter motor to get the engine cranking. When you turn the key in the ignition and hear a click or hum, it’s time to inspect the solenoid.

If a wire connecting your solenoid to your Big Dog mower grows hot and smokes or melts, that’s another sign your solenoid needs replacing.

Follow these procedures to ensure the solenoid in your Big Dog mower is working properly. If your solenoid is faulty, you should replace it.

Big Dog Mower with a Bad Charging System

A Big Dog mower’s inability to start may have other causes, but a weak battery brought on by the mower’s charging system is one of them.

In the event that the battery is not charged by the charging mechanism, the mower may not start when you want to use it.

There are a number of possible electrical components that could be at fault, including the stator or alternator. Test your battery charging setup using an ohm meter by reading this article.

If you suspect the charging system is at fault, the best course of action is to have a small engine mechanic inspect and diagnose the system.

It can get pricey if you try to guess what’s wrong with your mower and start replacing parts.

Big Dog Mower Wrongly Operated

Big Dog mowers are equipped with safety mechanisms that prevent them from starting unless the proper beginning procedures are followed.

To avoid activating the safety mechanisms that disable or prevent starting of your Big Dog lawnmower, check the manual to see if there are any special operating procedures you need to follow.

In order to start the engine on a Big Dog riding mower or zero-turn, the operator must first engage the brake and turn off the PTO switch.