Your Exmark mower requires three items for the engine to form combustion to start and run: air, fuel, and spark. When it receives spark and air but lacks sufficient fuel, the mower will run sluggish or not run at all.
An Exmark lawn mower isn’t getting fuel when old fuel develops a varnish and gums the fuel system; the fuel filter is plugged; the fuel line is clogged; the fuel pump is faulty; the carburetor is dirty, or the fuel cap is plugged.
When performing repairs, follow all safety procedures listed in the Exmark operator’s manual including 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.
Troubleshoot: Exmark Lawn Mower Isn’t Getting Fuel
- Check for bad or old fuel
- Check for a plugged fuel filter
- Check for a plugged fuel line
- Check for a faulty fuel pump
- Check for a dirty carburetor
- Check for a plugged fuel cap
6 Reasons Your Exmark Lawn Mower Isn’t Getting Fuel
Bad or Old Gas
Gas is often the root cause for a fuel problem to develop in an Exmark mower. This is because gas can begin to break down as soon as 30 days after purchase.
Most types of gasoline sold at fuel stations today contain ethanol. This is a product that isn’t good for the small engine on an Exmark. Ethanol attracts moisture to the fuel system that can leave behind varnish and gummy deposits restricting fuel flow.
This moisture can also prematurely corrode the fuel system components causing them to fail. These restrictions and component failures will keep the mower from getting the fuel it requires to start and run.
Use a fuel siphon pump to drain your fuel tank into a container to collect the old fuel.
Refill your fuel tank with fuel including a fuel additive to stabilize your fuel. I use Sea Foam Motor Treatment in my lawn mower. There are many advantages to using Sea Foam including cleaning the fuel system.
Read more about the right gas to use in your Exmark gas-powered lawn mower here. I further explain the effects of ethanol in addition to helpful tips to store and stabilize your fuel.
Plugged Fuel Filter
It’s important to run a fuel filter on your Exmark mower to strain fuel to keep contaminants out of the fuel system. While the filter serves a good purpose to protect the engine, it can also cause the engine to not run when the filter becomes plugged.
The fuel filter should be replaced annually or sooner if you use the mower for commercial purposes. If you don’t check the filter and change it out, it can become clogged with dirt and debris that has gotten into the fuel tank.
Replace a plugged fuel filter that is keeping your Exmark from getting fuel. When installing the new filter, pay attention to the arrow on the side of the plastic inline fuel filter.
The filter must be installed with the arrow pointing in the direction of the fuel flow. This means the arrow should be pointing toward the carburetor and away from the fuel tank.
Clogged Fuel Lines
The varnish left behind by old fuel in the fuel lines can develop deposits that can cause a fuel restriction. A good flow of fuel isn’t able to pass through the restriction keeping your Exmark from getting the amount of fuel it needs.
To find a clog in the fuel line, you will have to check each section of the fuel line. Use the fuel shut-off valve or fuel pinch-off pliers to crimp the fuel line to stop and start the fuel supply while checking the fuel flow through each line.
Once you find a section of the hose that is clogged, remove the hose from your mower. Spray carburetor cleaner into the hose to help loosen the clog. Blow out the line with compressed air. Repeat until you dislodge the clog and open the line.
If you are unable to unclog the line or the fuel line is dry and cracked, it’s time to replace your fuel line.
Bad Fuel Pump
An Exmark lawn mower uses a fuel pump when the carburetor is positioned higher than the fuel tank. The pump is required to work against gravity to pump fuel uphill to the carburetor.
Most lawn mowers use a vacuum fuel pump. This style of pump builds pressure off the crankcase to move fuel to the carburetor.
When the fuel pump cracks or fails to work correctly you will have to replace it. If you don’t see physical cracks or fuel leaking, you can take some steps to check the condition of the fuel pump.
Before you test the pump, make sure you are getting fuel to the inlet port on the pump. (If you are not, check for a blockage in the fuel line or fuel filter)
Once you have confirmed fuel flow to the pump, reattach the fuel line to the inlet port. Remove the fuel line from the carburetor and place it in a container. Check your pump is working correctly by starting your fuel flow and starting your mower.
You should have a steady or pulsating flow of fuel coming out of the fuel line. If you do not, you need to replace the fuel pump.
If your Exmark has an electronic fuel injection pump, obtain a pressure reading using a fuel pressure gauge. Refer to your Exmark operator’s manual for fuel pressure specifications. Replace the fuel pump if the pressures are lower than the specification required by the engine manufacturer.
Dirty Carburetor
The carburetor is responsible for mixing the right amount of gas with the right amount of air to form combustion. When the carburetor becomes dirty from old gas deposits, it may fail to get a sufficient amount of gas to the engine.
Small components inside the carburetor including the fuel jet, float, and float needle can become stuck or clogged restricting fuel.
To determine if you need to take the carburetor apart to clean it, make sure you are getting fuel to the carburetor. (Check for a fuel line clog, bad filter, or faulty fuel pump if you aren’t getting fuel to the carburetor).
Once you determine you are getting good flow to the carburetor, remove the air filter and spray the carburetor cleaner into the air intake. Next, start the engine to see if it will continue to run.
If your lawn mower starts and won’t continue to run, you will need to remove your carburetor and take it apart for cleaning. Check out this post for carburetor cleaning instructions.
Bad Fuel Cap
The pressure inside of the fuel tank must be the same as the atmospheric pressure outside of the tank. This is made possible with a vent located in the fuel cap.
When the fuel cap vent is clogged and no longer allows air to pass through the cap, the tank will form a vacuum. This vacuum will prevent fuel from moving through the fuel lines to the carburetor keeping the engine from getting fuel.
To determine if the fuel cap is no longer functioning, loosen the cap to allow air in the tank. The engine should start and run smoothly. Reinstall the fuel cap to see if the engine is starved of fuel after it runs for a while.
If it begins to run sluggish and then runs better once you loosen the cap again, you most likely have a bad fuel cap and it must be replaced with a new cap.
In Summary
To minimize problems developing in your Exmark mower’s fuel system, protect the fuel system by using fresh gas with low ethanol content. You should always use gasoline with a minimum octane rating of 87 and maximum ethanol content of 10%.
Consume gasoline within 30 days. If you purchased more gas than you can use within this time frame, add a fuel stabilizer to make gas last a little longer before it breaks down.
I always add a fuel stabilizer like Sea Foam Motor Treatment to every tank of fuel to minimize clogging, starting, and running issues in my lawn mower.