Fuel pump lawn tractor. How to Know if Mower Fuel Pump is Bad

My Lawn Mower is Not Getting Gas to Spark Plug [5 Fixes that Work]

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It is frustrating when your lawn mower won’t start. I’ve seen this problem even with new gas-powered mowers. After extensive diagnosis and experience, I’ve found the most common cause is that the lawn mower is not getting gas to the spark plug. But that’s not all.

When your lawn mower won’t start, chances are it is not getting gas to the spark plug. Common causes include a dirty air filter, spark plug, and carburetor. To fix these issues, replace the fuel filter, clean the carburetor and spark plug, and replace the fuel if it is old as illustrated below.

What causes my lawn mower not to pump gas to spark plugs?

Gas-powered lawn mowers need gas to be pumped into the carburetor in order to start. Should anything obstruct the flow of gasoline, the engine won’t start. And even if it does, it’s likely to fail after a couple of minutes.

Here’s what causes mowers to not efficiently pump gas to the spark plug and ignite:

A dirty air filter

The air filter on a carburetor cleans the incoming air of dust and other debris that could cause damage to engine parts. Over time, the air filter could get clogged up, thus affecting the flow of oxygen to the engine.

When the engine does not get enough oxygen that helps with fuel combustion when the spark plug ignites your lawn mower won’t start.

Manual choke left turned on

The choke is a shaft-mounted valve within the air intake chamber of the carburetor. Its function is to block the airflow for improved suction and consequently facilitate a more efficient engine start-up.

While some chokes are automatic, some mower motors have manual chokes that the user has to turn on and off by themselves.

If you leave a manual choke on several minutes after starting the mower, the carburetor will likely flood up, leading to starting failures the next time you try to start up your lawn mower.

Clogged filters in the fuel pump

powerful mowers, such as ride-along lawn mowers, make use of fuel pumps to pump gas into the engine – instead of the gravity-feeding system that’s common in most push-along mowers.

If the filters are clogged, your lawn mower won’t start because gas will not reach the spark plug.

Stuck open valves

If the intake and exhaust valves don’t seal fully due to sticking, build-up of debris or normal wear and tear, compression is hampered, consequently creating ignition problems.

If the intake valve becomes stuck, this affects the efficiency of the flow of the air/fuel mixture to the cylinder, resulting in a lawn mower that won’t start.

Signs your lawn mower is not getting gas

There are several issues that could be causing your lawn mower not to run, including electric faults within the spark plugs as well as the causes I’ve listed above.

For instance- if your spark plug is wet, you definitely can’t get your motor to start. However- more often than not- the issue is usually caused by the cutting off of efficient fuel supply to the spark plugs.

Here are a few signs your lawn mower is not getting gas to the spark plug and won’t start due to the inability to pump gas to the engine:

Lawn mower won’t start completely

If you totally can’t get your mower to start, there could be issues with the efficiency of fuel flow to the engine.

• This is usually caused by debris collecting and blocking crucial components of the fuel intake system such as the throttle, primer button, carburetor bowl, and the fuel filter.
• A malfunctioned fuel pump.

Such clogging hampers the efficient flow of gas to the spark plugs.

Riding lawn mower starts then stops running

If your fuel tank is full, but your mower still comes to a stop after just a few seconds, it’s highly likely that the hole atop the tank’s cap has been blocked by dust and debris.

This cuts off the back pressure needed to push fuel out of the tank and into the carburetor – by cutting off air supply into the tank.

No gasoline odor

If you can’t get your mower to start and at the same time can’t sense any gas smell coming from the motor, your lawnmower has definitely run out of fuel.

Most mower brands typically include a dipstick attached to the screw cap. A dipstick is used to check the fuel level within the gas tank. It will typically have low and high-level markers.

• Dip the dipstick into the gas tank to check the gasoline level.
• If the fuel mark is below the low-level mark, it means you’re running out of gasoline and that’s why your mower won’t start.

In this case, refill the gas tank then try starting the mower again to see if the problem will have been fixed.

See also my guide on the type of gas to use with your lawn mower

How to Fix a Lawn Mower that’s Not Getting Gas

Some of these problems can occur when in the middle of mowing. A dirty spark plug, for instance, may cause your lawn mower not to have enough power for mowing. Fuel pump and filter problems too can make it not to start.

Here are simple DIY fixes you can use to correct the problem and start the lawn mower again.

Use fresh or new fuel

I found that for Craftsman mowers, old fuel tends to clog up the carburetors and cause difficulty in the flow of gasoline. As such, you should always ensure that the gasoline in your tank is as fresh as necessary.

• A good way of keeping stored oil fresher for longer is to use a gas stabilization product.
• Use a high-quality fuel stabilizer for small engines such as the Star Tron Enzyme Fuel Treatment.

This solution will prevent fuel degradation by reducing oxidation. Your fuel will stay clean and fresh for longer.

Replace the fuel filter

If you own a Husqvarna mower and it won’t start, the most likely cause would be a clogged fuel filter. This usually happens if you’ve left fuel in your mower for long.

The best fix is to drain off the old fuel from the gas tank and replacing the filter.

Clean the carburetor

For MTD mowers, the most common cause of fuel not getting to the spark plug is a clogged-up carburetor due to the buildup of debris.

To fix the problem, clean up the carburetor by taking out the fuel bowl and spraying the carburetor with some carburetor cleaner.

A clean carburetor will get your MTD lawn mower motor running again.

Here’s a video on how to clean the carburetor on your lawn mower:

How to Know if Mower Fuel Pump is Bad

Maintaining your lawn mower is key to ensuring its longevity and proper functioning. One of the most critical maintenance tasks is keeping the fuel system clean. However, if you suspect that there might be something wrong with your fuel pump, how can you tell?

This blog post will discuss how to know if mower fuel pump is bad and what you can do about it.

• What is a Fuel Pump, and What Does It Do?
• How to Know if Mower Fuel Pump is Bad
• 1. Fuel Tank Noise
• 2. Priming the Fuel System
• 3. Sputtering Engine
• 4. Bad or Clogged Filter
• 5. Dead Engine
• 6. Power Loss
• 7. Surging Power
• FAQ’s symptoms of bad fuel pump on riding mower
• Can a Fuel Pump Be Bad Even If It Turns On?
• Is a Fuel Pump the Same Thing as a Carburetor?
• How Do I Know If My Lawn Mower’s Fuel Pump Needs to Be Replaced?
• Author

What is a Fuel Pump, and What Does It Do?

A fuel pump is a device that works to transfer gasoline from the tank or storage compartment into your mower engine. As it does so, it creates pressure to push the gasoline through.

Without adequate pressure, your lawn mower cannot function at its best, and you will encounter issues such as reduced throttle response time and bad running performance.

Power Loss

If you notice your lawnmower’s engine is powering down during use, it could be because of a faulty fuel pump.

This can happen for many reasons, although it shouldn’t necessarily mean that the pump has to be replaced if you haven’t experienced any other symptoms.

Surging Power

If you hear your lawnmower’s engine surging and losing power after refueling, this is most likely the result of a fuel pump that has failed.

A bad pump will cause unneeded pressure to build up in your mower’s fuel system and lead to severe problems if it isn’t fixed soon.

Again, it might be a good idea to check the fuel filter or line for excess gas if this happens after refueling.

It could also be a good idea to get your lawn mower serviced at your local small engine repair shop, especially if you haven’t experienced any of these issues before.

FAQ’s symptoms of bad fuel pump on riding mower

Can a Fuel Pump Be Bad Even If It Turns On?

Yes. A fuel pump can fail without any warning signs, so it’s always best to be prepared if you’re going to be working on your mower’s engine.

This is especially true if you’ve just refueled it and noticed symptoms.

Is a Fuel Pump the Same Thing as a Carburetor?

No. A fuel pump is used to get gas from your tank into your mower’s engine, where it is then mixed with air in the carburetor.

It should not be confused with the carburetor itself, which contains the fuel and air valves and other components to mix gas and air correctly.Dull mower blade symptoms

How Do I Know If My Lawn Mower’s Fuel Pump Needs to Be Replaced?

It might need to be replaced if you’re experiencing any of the above symptoms, as well as other issues such as severe stuttering or trouble starting.

It can be challenging to pinpoint precisely what’s causing trouble with your mower.

While it’s possible to test the fuel pump yourself, it might be a better idea to take your mower in for repair.

Not only will you save time and hassle, but you may also prevent further damage to your machine.

Author

Hi, I’m Ricky. I’ve been involved in lawn care and landscaping from when I was 15. To be honest, I didn’t like the idea of pushing mowers, collecting grass clippings, and maintaining flowerbeds at the time. But having seem the passion my parents had for gardening and outdoors and the effort they put in maintaining the health and beauty of our landscape, I couldn’t help but not only admire their hard work but also I became a part of it. As someone who loves to spend time with nature’s best, I find myself learning a lot more about gardening and outdoors on a daily basis. Not to mention I love to share the knowledge I’ve gathered over the years with my readers at We Mow Dallas. To be clear, I don’t have a Master’s degree in gardening or anything like that. Everything I’ve learned about gardening, landscaping, and lawn care spring from passion and engagement with my parents. And with a ton of free information out there, plus the ability to run tests and determine what works best for lawn care and landscaping, every day is an opportunity to learn and implement something new. My goal with We Mow Dallas is to teach you exactly how to maintain your lawn and landscape. And since I walk the talk in reality, you shouldn’t hesitate to join me in this wonderful world of landscaping and lawn care. View all posts

Lawnmower Won’t Start? Do this.

A lawnmower that won’t start, especially when taken from storage, is almost always due to one problem: bad gas.

Storing a lawnmower in the fall without adding gasoline stabilizer to the fuel tank can cause the fuel to break down and plug the fuel passages. If fixing that problem doesn’t help, there are a few others that can help fix a lawnmower that won’t start, as we explain here.

How to Fix a Lawnmower That Won’t Start

Replace the Bad Gas

Over time (like the six months your lawnmower sat in your garage over the winter), the lighter hydrocarbons in gas can evaporate. This process creates gums and varnish that dirty the carburetor, plug fuel passages and prevent gas from flowing into the combustion chamber.

The carburetor bowl below formed corrosion and deposits during storage, which can easily plug fuel passages and prevent the engine from starting.

Storing equipment without stabilizing the gas can lead to deposits that foul the carburetor or injectors.

Ethanol-containing gas can absorb water from the atmosphere, which can lead to phase separation, which occurs when ethanol and gas separate, much like oil and water. Ethanol that has absorbed enough moisture and has sat long enough can foul the fuel system and prevent the engine from starting.

No matter how many times you yank the pull cord and pollute the air with your advanced vocabulary, the lawnmower won’t start if it’s trying to run on bad gas.

In extreme cases, evaporation of lighter hydrocarbons can change the gasoline’s composition enough to prevent it from igniting. The gas may be fueling the engine, but it doesn’t matter if it won’t ignite.

Bad Gas in Your Lawnmower? Here’s How to Fix It

If you neglected to add gasoline stabilizer to the fuel prior to storage, empty the tank and replace with fresh gas. If the tank is nearly empty, simply topping off with fresh gas is often enough to get it started.

On some mowers, you can easily remove and empty the fuel tank. Sometimes that’s more trouble than it’s worth. In these cases, use a fluid extraction pump or even a turkey baster to remove the bad gas. You don’t need to remove all of it; but try to get as much out as possible.

Clean the Carburetor

You’ve replaced the fuel, but your lawnmower still won’t start.

Next, try cleaning the carburetor. Remove the air filter and spray carburetor cleaner into the intake. Let it sit for several minutes to help loosen and dissolve varnish and gums.

Remove the air filter and spray carburetor cleaner into the intake. Let it sit a few minutes to loosen deposits.

On some carburetors, you can easily remove the float bowl. If equipped, first remove the small drain plug and drain the gas from the bowl. Remove the float bowl cover and spray the float and narrow fuel passages with carburetor cleaner.

This kind of “quick-and-dirty” carburetor cleaning is usually all it takes to get the gas flowing again and your lawnmower back to cutting grass.

If not, consider removing the carburetor from the engine, disassembling it and giving it a good cleaning. Be forewarned, however: taking apart a carburetor can lead to nothing but frustration for the uninitiated. Take pictures with your phone to aid in reassembly. Note the positions of any linkages or the settings of any mixture screws, if equipped. If you’re at all reluctant, visit the servicing dealer instead.

Consider replacing the carburetor altogether. It’s a fairly simple process on most smaller mowers and it’s often less expensive than taking it to the dealer.

Direct compressed air from the inside of the air filter out to remove debris that may be reducing airflow and preventing the lawnmower from starting.

Clean/Replace the Air Filter

With the air filter removed, now’s the perfect time to clean it.

Tap rigid filters on a workbench or the palm of your hand to dislodge grass clippings, leaves and other debris. Direct compressed air from the inside of the filter out to avoid lodging debris deeper into the media.

Use soap and water to wash foam filters. If it’s been a few years, simply replace the filter; they’re inexpensive and mark the only line of defense against wear-causing debris entering your engine and wearing the cylinder and piston rings.

An incorrectly gapped spark plug can prevent the engine from starting. Set the gap to the specification given in the owner’s manual.

Check the Spark Plug

A dirty or bad spark plug may also be to blame. Remove the plug and inspect condition. A spark plug in a properly running four-stroke engine should last for years and never appear oily or burned. If so, replace it.

Use a spark-plug tester to check for spark. If you don’t have one, clip the spark-plug boot onto the plug, hold the plug against the metal cylinder head and slowly pull the starter cord. You should see a strong, blue spark. It helps to test the plug in a darkened garage. Replace the plug if you don’t see a spark or it appears weak.

While you’re at it, check the spark-plug gap and set it to the factory specifications noted in the lawnmower owner’s manual.

If you know the plug is good, but you still don’t have spark, the coil likely has failed and requires replacement.

Did You Hit a Rock or Other Obstacle?

We’ve all killed a lawnmower engine after hitting a rock or big tree root.

If your lawnmower won’t start in this scenario, you probably sheared the flywheel key. It’s a tiny piece of metal that aligns the flywheel correctly to set the proper engine timing. Hitting an immovable obstacle can immediately stop the mower blade (and crankshaft) while the flywheel keeps spinning, shearing the key.

In this case, the engine timing is off and the mower won’t start until you pull the flywheel and replace the key. It’s an easy enough job IF you have a set of gear pullers lying around the garage. If not, rent a set from a parts store (or buy one…there’s never a bad reason to buy a new tool) or visit the dealer.

My Lawnmower Starts But Runs Poorly

If you finally get the lawnmower started, but it runs like a three-legged dog, try cleaning the carburetor with AMSOIL Power Foam. It’s a potent cleaning agent designed to remove performance-robbing carbon, varnish and other gunk from carburetors and engines.

Add Gasoline Stabilizer to Avoid Most of These Problems

Which sounds better? Completing all these steps each year when your lawnmower won’t start? Or pouring a little gasoline stabilizer into your fuel tank?

Simply using a good gasoline stabilizer can help avoid most of the problems with a lawnmower that won’t start.

AMSOIL Gasoline Stabilizer, for example, keeps fuel fresh up to 12 months. It helps prevent the lighter hydrocarbons from evaporating to reduce gum and varnish and keep the fuel flowing. It also contains corrosion inhibitors for additional protection.

I have a five-gallon gas can in my garage from which I fuel two lawnmowers, two chainsaws, two snowblowers, a string trimmer, an ATV and the occasional brush fire. I treat the fuel with Gasoline Stabilizer every time I fill it so I never have to worry about the gas going bad and causing problems.

You can also use AMSOIL Quickshot. It’s designed primarily to clean carburetors and combustion chambers while addressing problems with ethanol. But it also provides short-term gasoline stabilization of up to six months.

Use a Good Motor Oil for Your Lawnmower

Although motor oil has no bearing on whether your lawnmower starts or not (unless you don’t use oil at all and seize the engine), it pays to use a high-quality motor oil in your lawnmower.

This is especially true for professionals or homeowners running expensive zero-turn or riding mowers.

Lawnmower engines are tougher on oil than most people realize. They’re usually air-cooled, which means they run hotter than liquid-cooled automotive engines.

They often run for hours in hot, dirty, wet conditions. Many don’t have an oil filter, further stressing the oil.

In these conditions, motor oils formulated for standard service can break down, leading to harmful deposits and reduced wear protection.

For maximum performance and life, use a motor oil in your lawnmower designed to deliver commercial-grade protection, like AMSOIL Synthetic Small-Engine Oil.

Its long-life formulation has repeatedly demonstrated its ability to safely exceed original equipment manufacturer (OEM) drain intervals in the toughest conditions. It provides an extra measure of protection when equipment goes longer between oil changes than is recommended by the OEM.

What to Do When a Tractor Is Blowing Black Smoke and Has No Power

It can be frustrating when any piece of machinery doesn’t work. This is particularly true if it is a tractor that you are trying to use to accomplish a specific task. If your tractor is blowing black smoke, this is a very common problem that you can address.

Causes of black smoke from a tractor with loss of power:

Any of these issues can cause your diesel tractor to lose power and exhaust black smoke. Let’s look at each of these causes and how to address them, but first, understand this:

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What Does Black Smoke Mean Coming From a Tractor?

A diesel tractor can produce different colors of smoke and they can cause your tractor to run rough. Typically, the smoke is white, black, or blue. The most common color is black. When black smoke is coming out of your tractor, this means that there is an imbalance in the air-to-fuel ratio within the machine.

There is either too much fuel being added or not enough oxygen being put in to burn the fuel. When you see black smoke, what you are seeing is a smoke full of particulates. These particulates are large particles of diesel fuel that are not being properly burned.

Normally, when the exhaust exits the engine, the byproduct should be a combination of water and carbon dioxide.

The diesel fuel is chemically made up of long chains of carbon molecules, and combustion breaks down these molecules. If there is something wrong in the combustion process, the chemical reaction will leave long tail hydrocarbons completely intact, which is what you see when black smoke is emitted (source).

This all sounds very sciency but it matters. When a diesel engine is putting out black smoke, it will not be getting the maximum power and fuel mileage (source).

Causes of Black Smoke From a Tractor?

If we are going to fix it, we need to figure out the cause of the black smoke. The fix will depend on what’s wrong so let’s look at each issue one at a time.

Faulty Injector

If your fuel injector gets dirty or clogged, this can be the cause of black smoke and a loss of power. The purpose of a fuel injector is to supply your diesel engine with fuel (source). The injector sprays fuel into the engine’s cylinder via a nozzle to start the fuel combustion process.

There is an Engine Control Unit, or ECU, that manages several individual components of the engine, including the fuel injector. This is how the fuel injector is controlled so that it sprays fuel at the right time and in the right amounts.

If the injector is spraying more fuel than necessary, this can lead to black smoke. In some cases, the fuel injector could be leaking or broken, which can cause the aforementioned changes in the air-to-fuel ratio.

In this case, you will need to get the fuel injector either cleaned or replaced.

Before disassembling though, consider using Sea Foam (link to Amazon) to clean the fuel injectors.

This video from the manufacturer walks you though how this is done. Although they are demonstrating on a diesel truck, the process is the same for a tractor.

The combustion process involves both diesel fuel and air. If the engine isn’t getting enough air, this could be the cause of black smoke. This is one reason why you would need to check the air filter.

If it is dirty or clogged, this could be the reason why enough air isn’t getting in. In this instance, you just need to replace the air filter (source). If this doesn’t work, the problem lies somewhere else.

Bad EGR Valve

The Exhaust Gas Recirculation, or EGR valve, is there to improve your engine’s economy and performance. It also allows exhaust gases to flow back through the cylinders to be burned again, cutting down on overall emissions.

It’s typical for people to experience performance problems with their engines if the EGR valve is clogged or malfunctioning. This is because the air-to-fuel ratio is off, which you already know is true because of the black smoke. Generally, there will be reductions in fuel efficiency, accelerations, and overall power of the engine.

If this is the case, you will need to have the EGR valve replaced. When you do this, you will want to make sure that the whole system is running smoothly (source).

This means you will want to clean all of the carbon deposits off of the EGR pintle, clear all of the trouble codes, inspect the vacuum hoses that are connected to the valve, have an EGR transducer test done, and test the new valve to make sure that it is operating properly.

In order to minimize the number of times that you will have to change the valve, you will want to maintain the EGR valve properly. From time to time, you should have an air induction service done on your tractor, since it will clean all of the carbon and sludge out of the air intake system.

Regular oil changes will be helpful as well since they will minimize the amount of sludge accumulated in the engine.

Bad Turbocharger

The turbocharger is very important for your tractor. It’s a compressor that is located on the exhaust side of the vehicle, and it enhances the horsepower of your tractor.

It drives air into the engine as the RPM of the engine goes up (source). Ultimately, it increases power. This is why if you have a bad turbocharger, this can lead to black smoke and a loss of power.

If this is the case, you will need to have your turbocharger repaired or replaced.

Conclusion

When some people see black smoke coming out of a tractor, they may not take it seriously at first. However, it’s always a good idea to pay attention to these issues.

Even if it doesn’t seem to be causing problems at first, if you don’t address it, it can get to the point where your tractor has no power.

Most of the time, black smoke isn’t a terrible sign for your tractor. Most of the underlying problems, in this case, are not that difficult to fix. You just need to diagnose the issue and go from there.

eManualOnline provides descriptive, affordable and convenient service and repair manuals for cars, trucks, tractors, motorcycles, and more. Download one today. (link to eManual Online).

If you are wanting a broader explanation of black smoke causes in a diesel engine, see this video from Bell Performance. They also delve into white smoke causes compared to black smoke.

Thriving Yard aims to simplify the unnecessarily complex process of growing and maintaining a healthy, thriving lawn and garden. Unlike corporate website companies who write articles from an office overlooking a major city, the authors on this website live in small towns and regularly use many of the tips and recommendations provided in their own garden and lawn care. Read