Riding lawn mower troubleshooting. Here s Why Your Lawn Mower Won t Start And What To Do About It

Troubleshooting Lawn Mower Starting Problems

The air is warmer and the grass is growing – time to break out the lawn mower. Unlike your car, your lawn mower and other lawn and garden equipment are not used regularly and the time spent sitting in storage can lead to problems with them running properly.

When you take your mower out for the first time, you may encounter a variety of situations. If you are lucky, the lawn mower will start with the first pull of the cord. Unfortunately, after months of sitting around, it is likely your lawn mower may not run smoothly, or even start at all. Before you give up, here are some things you can do to troubleshoot the problem.

Causes of engine trouble

If your engine starts but does not run smoothly or doesn’t start, the culprit could be air intake or fuel system related. The problem could be the age of the fuel in the tank, dirt or debris in the carburetor or an obstructed fuel tank vent. Other causes could be a fouled spark plug or a dirty or clogged fuel filter that restricts the amount of fuel getting to the carburetor.

Change the gasoline

If this is the first time you have tried to start the engine since last fall, fresh fuel may be in order. Gasoline will go bad in as few as 30 days, especially when fuel is mixed with ethanol as it is in many areas. Ethanol attracts moisture and over time the moisture will dilute the gas.

If the fuel is old, it should be dumped into a container for proper disposal and fresh fuel should be added. Fuel additives are readily available wherever auto parts are sold and may be helpful in not only starting your engine, but also in cleaning out any gum or varnish deposits in your carburetor while the engine is running.

After adding new fuel, check the gas cap. In many small engines, the gas cap also has a vent that serves as the fuel tank ventilation. In order to work properly and supply a sufficient amount of fuel to the carburetor, the vent must be open and free of any debris.

Check the air filter

The job of the air filter is to remove dirt and debris from the air before it enters your engine. The filter may become clogged and not allow a sufficient amount of air into the engine for it to run smoothly. If the filter is dirty, it should be replaced.

Examine the spark plug

A dirty or fouled spark plug can cause your lawn mower to not start. It can also work itself loose, causing issues. If the spark plug appears to be seated correctly but the engine doesn’t start, a new one may be in order. For a few dollars, this easy fix can get your small engine working again. Be sure to use the correct replacement spark plug designed for your lawn mower.

Check the oil

Check the amount, color and consistency of the oil. If it appears dark black, change it. If the oil level is low, add the proper oil, identified by your owner’s manual, to the engine – but be careful not to overfill it!

Look at the Fuel Filter

The fuel filter keeps dirt and contaminants in the fuel from getting into the carburetor. If it becomes clogged, it can prevent a sufficient amount of fuel from passing into the combustion chamber, preventing your engine from starting. Check the fuel filter, replace it if it is dirty or clogged.

I’m still having issues with my mower – what should I do?

If you are still having problems, it might be time to take it to a small engine repair shop to have a mechanic look at it. With their expertise, they’ll get to the bottom of the problem in no time.

Learn more about Champion parts, find your car part, or find where to buy your auto part today.

The content contained in this article is for entertainment and informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content.

Here‘s Why Your Lawn Mower Won’t Start And What To Do About It

Standing in your garage with a dead lawn mower, a phone browser open to Google, and the vast untamed landscape of small engine troubleshooting before you, it can be easy to get discouraged. After all, just about anything that prevents a lawn mower from running well can also prevent it from starting. Let’s simplify all these possibilities and zero in on common starting problems, and ones that you’re likely encountering.

Of course, your situation could include all manner of devices thought of as mowers. You could have a simple push mower, or maybe an electric start push mower. But, you could also have a riding mower, an electric mower, or a zero-turn mower that costs more than a Chevrolet Spark. You might even have a tractor towing a rotary cutter like a Bush Hog, in which case you’re probably not reading this article. We’re going to take a look at the most common: push mowers and riding mowers. Your electric mower is essentially always started, and your licensing agreement might prohibit your working on your own tractor. We also won’t deal with zero-turn mowers directly, but obviously a lot of the info for small engines in general will apply to zero-turns. Let’s dive into some of the reasons your mower may not be starting, and what you should do about it.

Ignition system problems: spark plugs

At some point — possibly when the words we have ignition from the Kennedy Space Center Firing Room — many of us began to think of the word ignition as synonymous with starting, but that’s not exactly what’s going on with ignition systems. An ignition system is actually about producing a spark that ignites a fuel-air mixture within an engine’s cylinder(s). Ignition happens continually when you’re using a mower. A few components of this system can be culprits when an engine won’t start.

The most common culprit is probably a spark plug that needs cleaning or replacement. Buildup from a constantly exploding engine cylinder will eventually degrade the performance of the plug until it can’t function properly at all. It’s a little easier to diagnose a bad spark plug in an engine that will barely start than one that won’t start at all, and if you’ve recently noticed that your mower makes you pull the starter rope harder, is prone to losing power while running, or starts using more gas than normal, the plug might be the problem. The clearest sign of plug trouble is when your engine will turn over but not actually start.

It’s a good idea to replace them at least once per year, and cleaning or replacing your plugs is a reasonable first step in resolving just about any starting problem. You can try gently cleaning a spark plug with fine-grit sandpaper, a file, or a soft wire brush, and you can use carburetor or plug cleaning spray to help. Just be gentle; damaged plugs will not be kind to your engine. There are other potential plug issues (wrong plug, bad gapping, or a cracked insulator) that might not be worth diagnosing, given that replacing the plug with a new (and correct) one addresses all these issues at once.

Ignition system problems: plug wires and coil

After dealing with the plug, it’s just about time to get serious with your diagnostics. But first, inspect your plug wires for obvious wear or damage. If they appear to be in poor shape, they probably are, which makes replacing them a good idea regardless of whether they are the full cause of your starting troubles. Next, it’s time to verify that your engine isn’t getting a spark. Ground your plug’s threads against a metal part of the engine itself and have someone attempt to start the mower as you observe the plug. If you consistently don’t see a spark, you should start looking at other possible causes.

If your plug wires are in good shape, ensure they’re making good contact with the spark plugs. Clean their terminals and, if necessary, squeeze the terminals slightly with pliers. If your mower has an on/off switch, use an electrical tester to make sure it’s functioning. Switches on mowers with pull cords can be slightly tricky to diagnose, so it might be a good idea to check the on/off function with a multimeter set to continuity mode. The point is that the continuity should change when the switch changes from on to off; some switches might close a circuit when on while others might open the circuit, but there should definitely be a change when the switch, well, switches. Check that the coil control wire connecting the engine to the coil isn’t abraded; if it shorts to the engine, the mower won’t start or run. Finally, consider replacing the coil. These are not user-serviceable, but they are affordable and critical to starting and running your mower.

Batteries die for a living

By far the most common element of the ignition system that can prevent a riding mower’s starting is the battery. Almost 20% — 11.8 million — of Google’s search results for the word battery include the phrase dead battery, because that’s what batteries fundamentally do: expend all their energy and die. And lawn mower batteries are almost always flooded lead acid batteries, which die more easily and more thoroughly than any other sort.

A lot of the work of fixing a battery problem is the same as properly maintaining the battery to begin with. That is, it’s stuff you should do regularly anyway. So, clean the battery terminals with a wire brush (clamp-on terminals might require a special type of brush, often cone-shaped). Use battery terminal cleaner if it’s necessary, though it rarely is. Make sure all electrical connections are clean and tight. Batteries that haven’t been maintained with a trickle or Smart charger while in storage, such as over the winter, will probably need to be charged and will sometimes even need to be replaced. If your battery is in good condition, check out your alternator and starter. Testing an alternator is simple on equipment with working headlights, as many riding mowers have. Just observe the lights. If they don’t dim when you turn off your engine, you probably have an alternator problem.

After verifying that you have a fully charged battery and a working alternator, check all the wires connected to the alternator and starter for damage. (You can test them with a multimeter if you’re suspicious of their condition.) If everything else checks out, test your solenoid and starter switch using the procedures outlined in this Briggs Stratton guide.

Fuel troubles

Every now and then you’ll see news about a possible perpetual motion machine devised in a scientist’s lab (or mind), but until you can pick one up at Home Depot, you’re going to be dealing with fuel for your lawn mower. This usually means gasoline, and there are a few common points of failure small engines can experience when trying to get fuel from the tank to where it’s needed for internal combustion.

First, make sure you have gas in the tank to begin with. This gets overlooked more often than you might guess, especially when you’re already half-expecting other mower problems and your brain primes the pump by framing everything in that context. Next, examine the age of the gas in use. Did you buy the mower used? Has it been in storage for more than a couple of months? Has the gas itself been sitting in the gas can for a while? Gas can go south in as little as a month, so if someone’s telling you it can sit for two years (a common number in mower lore) without chemical assistance or consequence, you should take your maintenance advice from someone else.

Mowers should be stored without gas or with an added fuel stabilizer (the aforementioned chemical assistance), to prevent such issues. Old gas clogs and damages fuel lines and carburetors, and won’t start an engine very well even if it makes it to the right place. If you already have old gas in your mower, you might need to remove and clean the fuel system components, as described here by Simple Green.

Fuel troubles: the fuel system

Replace your fuel filter regularly, especially if you’ve had old gas in your engine. If your engine has a fuel pump — and it probably does — it will reside between your fuel tank and the carburetor. When you’re out of options, check that it’s actually pumping by using a guide, like this one from Hello Practical.

There’s also the possibility that you aren’t availing yourself of some aids many lawn mowers have built into them to ensure the proper fuel/air mixture makes it to the engine. First, there’s the priming bulb: usually a clear, rubbery protrusion near the carburetor you can press. It will fill itself with fuel, injecting the fuel system with additional fuel as needed for starting.

You should also learn to use your engine’s manual choke feature properly, if it has one. Many newer engines have an automatic choke, and mowers generally have either a choke or a priming bulb, as they both perform the work of enriching the fuel/air mixture for starting your engine. Start your engine with the choke on, then move it to the opposite position once the mower is running properly. Leaving the choke on will stall or potentially damage the engine. Also, check to see if the tiny hole in your gas cap is clogged. That hole creates a vent to allow fuel to move down the fuel lines, and if it’s clogged, your engine will be starved of fuel.

Air filters

Of course, when it’s time for things to blow up inside your engine’s cylinders, gas is only half of the story. Your choke (if you have one) tells the other half: You also need air to mix with the gas, and some mechanisms to help with the mixing. The choke makes the fuel/air mixture richer by restricting (temporarily) the flow of air through the carburetor. Once the engine is running, you should return the choke (and, thereby, the airflow) to normal. But there are a few possible reasons you might continue to have airflow problems.

The first is a dirty air filter. Like most parts of a lawn mower, the air filter is prone to becoming filthier than seems possible. This means it’s doing its job, and it also means the filter requires cleaning or replacing from time to time. A dirty air filter will cause an engine to misbehave in all manner of ways, including not starting easily or at all. Your mower has one or two filters, any of which may be either foam or paper. It’s usually better to replace a paper filter if possible, but otherwise tap it against a hard surface and blow it out gently from the inside with an air compressor.

Foam filters are a bit more involved. Start by tapping and blowing it out like a paper filter, then spray it thoroughly with a filter degreaser and allow to soak for 15 minutes. Rinse under clean running water and allow it to dry, and then apply a filter oil spray. To the extent it’s possible without damaging the filter, squeeze the filter to work the oil throughout. After a few minutes, reinstall the filter and wipe away any excess oil.

air: carburetor

Sometimes your fuel/air mix is off because the carburetor isn’t doing its job properly. In extreme cases, this could prevent the engine from starting. At that point, you must choose between cleaning and rebuilding the carburetor. Fortunately, these processes are mostly very simple. The standard process for cleaning a carb is to remove and clean (or replace) the air filter, then inspect the carburetor inside and out for stray debris. Finally, spray carburetor cleaner into the carburetor while the engine is running, per directions on the spray can.

If this doesn’t work — perhaps because the gum and gunk inside the carburetor is extreme as a result of age or being run with old gasoline — removing and rebuilding the carb isn’t as scary as it sounds. It’s basically a process of taking the carb off and then cleaning everything off of it that you can. It’s also a good idea to take some photos along the way, so you can be sure of how everything goes back together. Finally, just reassemble. Briggs Stratton has a good online overview of this process.

If this makes you too nervous, try adding a cleaning mixture of 4 ounces Sea Foam Motor Treatment and 8 ounces gasoline to the tank. Remove the spark plug(s) and then prime and crank or rope-pull the engine to draw the mixture into the carb. Allow it to sit 24 to 72 hours, then run the engine per Sea Foam’s instructions.

Odds, ends, and tips

There are a few other fairly common situations that can interfere with starting a mower. It’s never a bad idea to change your oil, but be sure to do it properly. Old oil, insufficient oil, overfilling with oil, or using oil that’s the wrong weight (viscosity) for the temperature outside can all contribute to difficult starting.

Keep your mower deck clean; an overabundance of grime and debris can slow blade rotation and hinder starting. Similarly, if you’ve run into something recently with your mower, inspect the mower deck to make sure the blades can rotate freely. A blade striking the deck can prevent the mower from starting altogether.

Finally, there’s the unpleasant business of the starter rope — that thing you yank on a mower with a recoil starter. There are two types of mower owners: those who have cursed the fortunes and questioned the character of mower manufacturers for inventing the recoil starter, and those who haven’t used a recoil starter at all. Common causes of starter rope problems include overfilling with oil and debris interfering with rotation in the mower deck, as mentioned above. Similar problems include bent mower blades and damaged mower deck shrouds. The cord may also be difficult to pull because the flywheel brake (controlled by a bar you must hold while using the mower) is stuck. Try loosening or tightening the cable, then repeatedly open and close the bar that engages the flywheel brake. If this doesn’t work, you might need professional assistance. If you feel up to it, Briggs Stratton has flywheel brake replacement instructions. Similarly, a hydrolocked engine (one that has seized after getting water in the engine) will normally require professional help, unless you’re up for these steps from Garden Guides.

Problems that aren’t (exactly) problems

Sometimes you’ll hear that the cause of some problem is a feature and not a bug, but the distinction isn’t helpful if you can’t start your lawn mower. The best example of this is a mechanism called a safety interlock (or often safety switch), by which your mower won’t run because some other thing isn’t quite right. For example, riding mowers that won’t start unless you’re sitting in the seat. Some cars have interlocks that prevent you from operating them if you’ve had a few beers, but fortunately mowers don’t have this feature yet, as it would prevent about 90% of Saturday afternoon lawn mowing from happening at all.

The safety switches on most riding lawn mowers include a seat switch that will not allow the engine to run unless the seat is occupied; a PTO safety switch that might prevent the blades from turning in certain situations and prevent the mower from starting when (for example) the blades are engaged; a brake switch to keep the mower from starting unless the brake is applied; and a reverse switch, that prevents mowing. Obviously several of these can prevent an engine from starting if they malfunction.

It might be tempting to disable some or all of these safety switches. Don’t — they’re there for good reasons. Unless you’re handy with a multimeter and circuits, dealing with faulty safety switches might be another job for a professional.

Troubleshooting guide

So, how do you know which of these problems is preventing your mower from starting? Let’s look at a few questions that will help you narrow down the most common problems and their solutions. If your mower is full of fuel but only runs for a few seconds, check the pinhole vent in your gas cap for obstructions. This could also be a sign of old gasoline. If the engine hasn’t been run in more than a month, treat the gas as suspect. You might also clean the carburetor and clean or replace the spark plug(s).

If your engine sounds like it’s cranking, but won’t fully turn over, you might have an electrical problem — possibly the starter. If you hear a clicking sound but nothing else, that similarly suggests starter, battery, or related problems. If you don’t hear anything at all when you turn the key, check the starter solenoid and its connections. This also might indicate issues with the battery, coil(s), ignition switch, or safety interlocks. Hearing nothing at all could also indicate that your mower is refusing to start because it is low on oil.

If the engine is cranking slowly, you probably have a failing battery. Check the battery and alternator. If your pull cord is difficult to pull, check that the flywheel brake is disengaged. Be sure you don’t have too much oil in the engine, and that it’s the correct weight for the season. Another sign the engine might be overfilled with oil is the presence of blue or white smoke when it does run. Black smoke, on the other hand, indicates the fuel mixture is too rich. Replace the air filter and check the choke mechanism.

How to fix steering on a riding lawnmower? Try these troubleshooting steps

Handling and steering are one of the key mechanisms in riding lawnmowers. Perfect handling allows you to make accurate turns in your garden, thus improving the overall turf finish. It makes mowing comfortable and enjoyable. If your steering wheel drifts by itself towards the right or left or has excessive vibrations and a play in it, then you may need to troubleshoot your steering mechanism. For this purpose, this blog post provides you with all the knowledge and expertise needed to fix the steering on a riding lawnmower.

How to fix steering on a riding lawnmower? Try these troubleshooting steps:

• Step 1: Prep the lawnmower for repair by parking it on a flat surface and turning the ignition off.
• Step 2: Check the tire pressure. If it seems too low, fill the tires with air.
• Step 3: Check the steering gear by opening the steering support bolts.
• Step 4: Replace the damaged bushings
• Step 5: Replace damaged bearings, shafts, and washers that are a part of the steering assembly.
• Step 6: Check the drag linkage that connects the tie rod with the gear sector.
• Step 7: After the fixes have been made, test the lawnmower for performance.

Steering problems can be caused due to various issues. If the tire pressure in the mower is too low, you might face difficulty in making turns. The steering shaft or the steering support assembly might have been worn out, resulting in problems. Furthermore, the mower’s drag linkage might have become loose, contributing to play and vibrations in the steering wheel. Luckily, the steering adjustment is not a tedious task and can be performed by yourself, provided you follow the steps correctly.

We recommend going through the entire article to understand better the repair procedure needed to fix the steering wheel on a riding lawnmower.

Fixing the Steering on a Riding Lawnmower, Step-by-Step:

Please follow the procedure mentioned below to fix the steering mechanism on a riding lawnmower.

Step 1: Perform initial measures:

To start, you need to prepare the lawnmower by performing some initial preparations.

• Park your mower: For this, you need to find a flat surface and park your mower there.
• Remove the spark plug cable: Disengage the mower blades by pulling the lever. Also, take the ignition key off. Disconnect mowers spark plug cable as well. This is a safety measure to ensure that the mower can not unintentionally start.
• Set the wheels straight: After that, adjust the mower’s wheels. Adjust the steering wheel so that the wheels are pointing forward. The steering wheel should be at its default center position.

Step 2: Checking tire pressure:

It can be challenging to steer if the tire pressure is not correct. If the pressure in tires is low, it will be tough to navigate the riding lawnmower correctly. Check the tire pressure on all wheels. Use your mower’s operator’s manual to check the tire pressure.

Use a pressure gauge to check the pressure as well. The reading in the tires should be as mentioned in the manual. Fill them up or release air from the tires until they match the amount of pressure in psi as suggested in the manual.

Step 3: Checking steering gear:

The steering gear is one of the essential things that allow us to steer. If it is damaged or broken, then you will face issues in steering. The whole steering system is controlled by steering gear. The steering gear can dislodge if you hit a tree, rock, or brick while mowing.

A bolt holds this steering gear. You need to loosen that bolt and then turn the steering wheel entirely to the left. The equipment will produce a popping sound on returning to its original position. After hearing that sound, tighten the bolt back. It indicates that the gear is broken and you need to replace it with a new one.

Step 4: Replacing the damaged bushings:

The bushings are present underneath the steering gear and are used to hold the bolts in place. Damaged bushings might lead to vibrations in the gear shaft.

To replace it, you need to remove the nut that holds the gear sector. Take the gear sector off the machine and then remove the bushings. After inserting the new one, reattach the gear sector and tighten the nut back as well.

Step 5: Replacing damaged lawnmower bearings, shafts, and washers:

Bearings, rods, and washers are not huge. Still, they play a vital role as structural members in the steering mechanism of a lawnmower. If they seem damaged or worn, you might face steering issues.

– Lawnmower Bearings:

Bearings allow the wheels to turn on the shafts by providing ample lubrication. The shaft might oscillate eccentrically if the bearings are damaged.

• Step 1: First of all, to replace it, remove the dust cap and snap the ring that is holding the wheel.
• Step 2: Remove the wheels and take the bearings out from the axle.
• Step 3: The bearings use grease to run smoothly. Grease them from both inside and outside. Also, use the lubricant on the inside of the wheel.
• Step 4: Reinstall the wheel after you are done.

– Lawnower Shafts:

The shafts provide rotatory motion from the steering wheel to the gearbox. If these are damaged, you need to replace them as well.

• Step 1: First of all, remove the mower deck, steering wheel, sprocket, and gas tank.
• Step 2: Using pliers, remove the steering shaft’s spring clip by lifting the mower’s front end.
• Step 3: Remove the post holding bolts, slide the washers, and remove the old shaft.
• Step 4: Check the washers as well. If they are broken, then you need to replace them.
• Step 5: After replacing the shaft and washers, reinstall the bolts and slide the shaft up through the bushing.
• Step 6: After lowering the mower down and inserting spring clips, reinstall the fuel tank.
• Step 7: Finally, reattach the steering wheel and tighten it correctly.

Check the following links for some guidance:

Step 6: Checking the lawnmower linkages:

Linkages are rods that are attached to the steering box. They are connected in different ways depending upon the mower’s model. To replace them, you need first to check the model of your lawnmower. Any damage to these linkages affects your mower’s steering. So they need an immediate replacement. For this, you need to find the mounting points of connection. There are bolts present at each end. Remove these bolts and install a new linkage.

Step 7: Testing the lawnmower:

After you have wholly followed the step-by-step process now, you need to test drive your mower. Start your mower as usual. Start moving your mower around. Check the steering of the lawnmower and see if it is fixed. The problem should be gone if you have followed the steps mentioned above.

Some Precautionary Measures:

While repairing or inspecting a lawnmower, you should always take care of safety precautions. It keeps you safe from any incident. Some of the precautionary steps that you should follow are given below:

• Use safety gloves throughout the procedure when you are dealing with sharp parts
• Turn off the ignition and disconnect the spark plug cable as mentioned earlier.
• Use sturdy shoes.
• Use lubricants to loosen screws and bolts.

Frequently asked questions:

The Lawnmower steering wheel is a bit loose; what to do?

If your steering wheel is a bit loose, then you need to replace some essential things. If the steering is loose and the wheel is not moving, then you need to replace the tie rod. Follow the video below if you need any help.

What should be the correct tire pressure for my lawnmower?

Correct tire pressure is important for steering. If the tire pressure is not accurate, it will affect the wheels’ traction and thus make it harder for them to complete turns. The Tire pressure of lawnmowers is generally measured in pounds per square inch (PSI). The factory setting for a standard riding lawnmower is 10 PSI for the rear and 14 PSI for front tires. Please check the owner’s manual to get a better grasp of the acceptable pressure values. 2-3 PSI difference is also acceptable.

The Front-wheel of my lawnmower is angled out. What to do?

If you notice that your riding lawnmower’s front wheels are angled out a bit, you need to fix them quickly because it can cause steering issues as well. It may be loose, so you need to repair it. Firstly, disconnect the spark plug to prevent accidents. Now, check the wheel’s mounting bolt. If it is loose, tighten it by using a wrench or replace it if it is broken.

However, if the wheel is broken, you need to replace it with a new one. Buy a new wheel from any hardware shop suitable for your lawnmower and replace it with the older one.

Final Remarks:

Steering is one of the most crucial mechanisms of a riding lawnmower. Fixing it is not as easy as fixing some other mower components. The parts and linkages associated with it are quite high in number. Hence, it is always tough to figure out which part is malfunctioning and hence, needs replacement. To avoid such problems with your lawnmower, always be sure that you drive it carefully and don’t bump into rocks and other obstacles, as this can loosen and damage certain components.

Riding Lawn Mower Won’t Start – Mechanics troubleshooting list

Riding mowers aren’t complex, and most problems can easily be fixed by the owner. I’ve covered all the most common faults here in this guide; you’ll be mowing in no time!

So why won’t your riding mower start? The most common reason for a riding mower cranking over but not starting is bad gas, but other possible reasons include:

Important – If your mower is not cranking over, you need to check out the repair guide – “Lawn Tractor Won’t Start No Click”.

What’s Cranking?

This is the turning of the engine by battery and starter power as you turn the key. It can be seen at the top of most mower engines as the flywheel spins around while attempting to start the engine.

The riding mowers used here for demo purposes may be different from yours, but no matter, the testing will be identical or very similar. At various points along the way, you will be directed to a solution for your problem, he said confidently.

I know this guide is long but don’t be put off; most of it will not be relevant to you.

Check The Basics

Doing some basic checks on your lawn tractor will sometimes solve the problem or at least point you in the right direction. The basics include oil level check; fuel level check; fuel tap on; air filter check; plug wire on; choke applied, and following the correct starting procedure.

Oil Level

Some tractor-mowers just won’t start if the oil level is low; it’s designed that way. It protects your engine from that Oooo moment.

It’s good practice to check the oil level every time you fill the gas tank. Check out “Does my mower need oil?”.

Gas

Is there gas in the mower? Sometimes the obvious is the solution. Was the gas fresh?

At my shop, I have found many strange concoctions – diesel, water, white spirits, vinegar, and of course, last year’s gas makes a regular appearance. Hey, we’ve all done it! Check out “Carburetor troubleshooting”.

Gas Tap

Some lawn tractors will have a gas valve, is it turned on? Gas valves stop the flow of gas to the carburetor and, if fitted, are usually turned off when the mowers are not in use. Check out “Lawn mower gas tap”.

Battery Charged

A strong healthy battery is critical to starting any electric key start lawnmower. A typical mower engine will only create enough energy for the spark plug to fire if the engine cranks over fast enough, around 350rpm min.

If your engine sounds like it isn’t cranking over at the usual speed, try jump-starting. This will rule out a weak battery. Check out “Tractor mower jump starting”.

Air Filter

A blocked air filter will prevent the mower from starting. The air filter needs to be kept clean; check it every 25 hours of use. Most mower filters are easy to access. Try starting your engine without the filter, but replace it as soon as possible if you find it’s the root cause.

Plug Wire

It’s easy for the plug wire to come loose, happens all the time. The wire usually lives right at the front of the engine, it’s a push-on fit, and as mowers vibrate a lot, the metal plug cap connection widens and becomes loose.

Choke

Most mowers will have a manual choke, and more modern mowers may be auto-choke. If you have a manual choke, you’ll need to set it to full to start a cold engine. Check out “How to start a lawn mower”.

Lock Out

All tractor-mowers will have lock-out or safety sensors fitted. As you know, they will stop the engine from cranking over or starting unless a set procedure is followed.

That’s all the easy stuff checked.

If you need one-to-one help, check out the JustAnswer Mower Mechanic link below, where you’ll chat directly with a mower mechanic within minutes. I earn a small commission for recommending JustAnswer mechanics, and I’m happy to do so; these guys are good, I know they’ll save you money.

Mower Cranks, But Won’t Start

Riding mower turns over but won’t start is the most common complaint I hear, and I usually hear it in the spring. Riding lawn mower engines are quite simple; they need three things to start:

Thing 1. Gas/Air MixThing 2. SparkThing 3. Compression

What is Gas/Air Mix?

Fuel is always at the top of the checklist. The reason fuel causes problems is that some fuels are ethanol-blended, fuels like e10. While small engine manufacturers say their engines run on these fuels, they would recommend you use regular gas, and the reason for that – is their engines were not designed to run on ethanol.

What’s Ethanol?

Ethanol is an alcohol fuel that is made from plants such as corn and sugar; this alcohol is then mixed with regular gas. Ethanol e10, which you see at the gas station, is 10% ethanol and 90% gas. E15, as you’ve guessed it, is 15% alcohol and 85% gas. E15 should never be used in small engines.

Ethanol burns hotter, and it’s thought the higher alcohol content is harmful to the rubber and plastic components of the fuel system. Using e15 fuel will invalidate your small engine manufacturer warranty. Ethanol fuels will turn stale after about one month; regular fuel will turn stale after three months.

The Problem With Ethanol

It attracts moisture; for cars, this isn’t an issue because the gas tanks are sealed, meaning the moisture can’t get in. Lawnmower fuel tanks are not sealed; they need to breathe. Moisture makes its way into the fuel tank, albeit in very small amounts.

This isn’t an issue when the mower is being used on a regular basis. The problem usually arises in the spring because, over the winter months, the alcohol in the carburetor evaporates and leaves moisture behind; this then corrodes and gums up the carburetor – Now it’s a no-start.

Gas Stabilizer

Fuel stabilizers were designed for gas-powered equipment that may sit for long periods between uses. As said earlier, regular gas will go stale in about three months. Ethanol fuels will go stale in one month; using a fuel stabilizer will keep these fuels fresh for up to two years.

If you choose not to use a fuel stabilizer – simply drain the fuel tank and run the mower until the engine stops. This should eliminate corrosion, gumming, and varnish build-up associated with stale fuel, but I prefer to use a stabilizer.

Check out Sta-bil fuel stabilizer on the “Small engine repair tools page”; it’s easy to use and will save you money in the long run.

Air Filter

Clean air is as important as fuel, however, is much less problematic. Filtering the air before it enters the engine is important as it prevents grit from damaging the carburetor and engine components, it also settles the air.

Most engine manufacturers make it easy for owners to quickly check the air filter. Filter covers are usually held on by plastic clips or simple wing nuts.

The filter should be checked and cleaned every 25 hours and, more often in dusty environments, replaced every 100 hours. Common filter types are pleated paper elements, fiber elements, and foam. Some air filters will have a pre-filter, usually foam, wrapped around the main filter; its function is to catch larger debris.

Paper and fiber elements can be cleaned using compressed air or banging them on the groundwork reasonably well. If the paper filters are oil or fuel soaked, they will need to be replaced as this blocks airflow.

Foam elements can be washed in soapy water and refitted when dry. Check out “Lawn tractor maintenance.”

What Is Spark?

When we talk about the spark, we’re talking about the whole ignition system. The spark is more than just the plug; the whole system comprises of, depending on how old the mower is: Battery; Starter; ​​Spark plug; Coil and Plug wire; Flywheel; Points; Ignition switch; Control module.

Battery

As you know, your battery must be in great shape; if it isn’t strong enough to turn the engine over fast enough, the flywheel and coil can’t make a good spark. As said earlier, you can rule out this as the issue by jump-starting the mower from your car, truck, or any 12-volt battery.

If you check out Battery Testing you’ll also learn how to test the battery; for this, however, you will need a voltmeter, but you can get one on this page “Small engine repair tools”.

Of course, the engine may be cranking over slowly for other reasons; if the weather is very cold, it causes battery performance to suffer. Using oil that’s too thick or overfilling can cause a slow crank speed.

A binding starter motor or, worse case, internal engine damage can cause a slow crank speed.

Spark Plug

If you have no spark, many times, it’s a failed spark plug. Having a spare plug that you can change out is useful for testing and minimizing downtime.

Removing the plug and checking its condition will usually tell you what’s going on inside the engine.

• Wet Plug tells you it’s getting fuel, maybe too much (Flooding)
• Black Oily plug could be a mechanical fault or simply too much oil in the engine
• Dry Plug could be a choke fault or blocked fuel system

In many cases, you can simply clean the plug, and you’re away mowing.

Using the correct plug is important; spark plugs have different thread lengths and have a particular heat range. Plugs are designed to run hot enough to burn off contaminants but not so hot that it pre-ignite (firing when they shouldn’t).

Fitting the wrong thread length and heat range can damage the engine. A quick check online with your engine manufacturer will give you the correct plug code.

Coil

The coil is where the voltage is created; coils will produce thousands of volts. They have a tough job, and they work hard in a hot location, right above the cylinder – it’s no wonder they are the next most common ignition component to fail.

Testing and replacing the coil is a simple job. Flywheels are a basic component and don’t give many issues. Points are fitted to much older mowers, they’re a serviceable item, but I won’t cover it in this guide.

Control Module

These are fitted to most modern mowers; they process the safety sensors signals and start/stop commands. In some cases, they are incorporated into the dash light panel. Most are basic printed circuits with resistors and relays.

Modules do fail and are vulnerable to moisture. Your mower may not have a control module; if so, the ignition switch does all the work. The advantage of not having a control module means the system is easier to fault find.

Ignition Switch

These are pretty basic and can be tested with a digital voltmeter. The number of pins at the rear of the switch will vary depending on the model. Ignition switches do fail, and terminals tend to corrode. We can test inputs and outputs and visually inspect for damage.

What Is Compression?

In simple terms, compression is the engine’s ability to build pressure in the cylinder without it leaking. As an engine gets older, the compression value reduces as compression begins to slip past worn sealing rings and valves.

To test this in the workshop, I used a compression tester. Modern engines have a compression release mechanism, which makes them easier to pull start. And so, on more modern engines, I use a leak-down test. This test pumps air into the engine and measures its ability to hold the pressure over a given amount of time.

My father was a mechanic too, and when he was serving his apprenticeship, car engines could only cover about eight thousand miles before needing some pretty heavy-duty maintenance. When I served my apprenticeship, car engines could easily do over 100 thousand before needing the same type of semi-major repair.

Some of the latest engines from Briggs and Stratton won’t ever need their oil changed; advancements in the design of engines and materials used are such that major mechanical failure is uncommon. Of course, misuse or lack of maintenance will cause failure.

Measuring Compression

Measuring compression accurately without the proper kit is impossible. However, there is an unscientific DIY test. This crude test will tell you if you have some compression, not an actual value.

If you prefer the correct tool for an accurate value, check out “Small engine tools” and look at the leak-down test kit.

With the plug removed and wearing protective gloves, put your thumb over the plug hole as a helper turns over the engine slowly. If you have compression, air will rush out past your thumb. If you’re looking for something a little more sophisticated, you’ll need a compression tester kit.

If your engine is lacking compression, suspect a sticking open valve. To fix a sticking valve – use a screwdriver to gently lever the spring into the released position. A sticking valve is a common complaint on engines that lay up for long periods.

Check out “Valve lash adjustment” it’s for a walk-behind mower, but the setup is identical.

The Gas Shot Test

To quickly find the problem, we need to narrow down the search area. Most nonstarting mowers are caused by fueling faults, and that’s why we start with the gas shot test. This test is an elimination round if you like. This test bypasses the fueling system, simultaneously testing the fuel system and the ignition system.

To run this test remove the air filter; you’ll need fresh gas. If the gas isn’t fresh, this test won’t work. Fill a bottle cap full of gas and drop it into the carburetor. Attempt to start your mower as normal with a full choke.

Gas shot – Begin with clean, fresh fuel. Remove the air filter cover and air filter (some will be fixed on with screws or wing nuts, others will just pull off)

Pour shot fresh gas into the carburetor, about a cap full. Now for some carburetor setups, this won’t be possible. And so, instead of removing the spark plug and using a funnel, pour gas straight into the cylinder, then refit the plug.

Turn-Key – Now attempt to start the mower in the normal way.

Result?

If the mower attempted to start or started – You have a fueling fault; move on to the choke system check below.If your mower made no attempt to start – You have eliminated a fueling fault, and your fault will likely be a lack of spark; you need to move on to the spark system check below.

The Choke System Test

OK, so you have identified a fueling system fault. In this next step, we need to be sure the choke system is working and being used correctly. Most riding mower owners already know this, but in my experience, lots of customers have never been shown how to start their riding mower correctly. And since cars don’t have a choke anymore, understandably, many owners aren’t familiar with a choke, what it is, and when they need to use it.

This post covers how and when to use coke – “How to start a tractor mower.”

Function

The function of a choke is to enrich the fuel mixture so a cold engine starts smoothly. The choke does this by restricting the amount of air entering the carburetor.

Gas engines run best when the ratio of air to fuel is 14.7 to 1. Meaning 14.7 parts air to 1 part fuel, also known as an air-fuel ratio (AFR). Using the choke counteracts the lean condition caused by the dense cold air.

Using Choke

Before you start your mower, move the choke lever to full choke, this is generally only needed on a cold engine. However, some engines may require a small amount of choke to start the engine, even when hot.

When the engine warms up, turn off the choke and move to full throttle. Check out “How to start a tractor mower.”

Test Choke Operation

Choke plates are usually operated by cable and will require adjustment from time to time. In this part of the guide, you will check if the choke plate is working correctly.

A choke that isn’t closing all the way will cause a no-start, and a choke that’s sticking “On” will cause poor running and black smoke.

If you can see the choke plate clearly when you remove the air filter, then you do not need to remove the engine cover. However, some engines will require the blower cover removed.

View the choke plate and note its position. Not necessary to remove this intake pipe. You can see into the choke plate to check its operation.

Carburetor was removed to show the choke “On” position.

Choke On – This is the correct position for starting a cold engine.

Adjust – If the choke plate is not moving to the closed position, adjust the cable so that it does.

If you found no issues with your choke system, check out “Carburetor troubleshooting.”

If you found no issues with your choke system, then your issue is most likely a dirty or contaminated carburetor. It’s a very common issue, and that’s why I have dedicated a separate page for it. Whichever carb problem you have, we’ll get it fixed here on the “Carburetor troubleshooting” Page.

The Spark System Test

If you have identified a likely spark system fault, then let’s test all the components of the system, beginning with the most common failures – plug; coil; control module (if fitted); ignition switch.

Have a new plug on hand, a helper, insulated pliers, and a plug removal tool. These tests are simple; however, take care to ground the plug against the engine securely, as the bad ground will lead to an incorrect diagnosis.

Alternatively, make life easy for yourself and buy the Ignition spark tester; you’ll find the type I use here on the “Small engine tools page”.

For this test, you will need a new plug, plug spanner, insulated pliers, and a helper.

Note: The best way to test the spark is with a spark tester tool, as it will load up and stress tests the coil.

Remove the spark plug and check the condition. Refit the plug wire and ground the plug on the engine.

Have a helper turn the key while you check for spark. Now try a new spark plug.

Result?

At this point, you have:

• Good spark – Check Compression.
• No or weak spark – Move on to the next step.

No spark or your spark is poor – you could have a faulty: Coil; Spark plug wire; Plug wire cap; Short circuit of coil control wire; or Faulty control module/Ignition switch.

Coil, also known as armature faults, are very common.

Look for obvious signs of damage. Arcing and corrosion of the plug cap, check it fits snugly and securely.

Chafing of wiring against the engine is common.

Remove the engine cover (blower cover) if not already removed. Locate the coil control wire connector. Remove the coil control wire; you may need pliers.

Now check for spark as you did earlier.

Result?

Do you have spark now?

• No, still no spark – Replace the coil. It’s faulty. (see fitting coil below)
• Yes, have a spark now – Check the coil control wire from the coil to the control module (or ignition switch) for chafing and shorting.

If you found no fault with the wiring (try wiggling) – Then go ahead and replace the control module. If your mower doesn’t have a control module fitted – then replace the ignition switch.

Fitting A Coil

Coil (also known as Armature) failure is common as these components work hard. Fitting a new one is a simple job; no special tools are needed. Only the engine covers need to be removed. When fitting the coil, an air gap must be maintained between the flywheel and the coil.

A feeler gauge is normally used to measure this gap. However, a business card also works. Fitting the coil is covered in the guide below.

Check out mower coils on the Amazon link below, which covers the most common types.

Remove the engine cover if not already removed.

Remove coil bolts, plug wire, and control wire connector.

Remove the coil control wire

Get quality parts; they are tested. Nobody likes revisiting the same job. Although coils all look pretty similar, they are different. Locate your coil part number and reference it when ordering.

An air gap must be maintained between the coil and the flywheel. A business card is just the right thickness. Tighten the bolts while pushing the coil towards the flywheel. Remove business cards by turning the flywheel.

Nice work, now rebuild in reverse order; you nailed it!

The Shear Key

The Shear key is a small piece of metal that’s designed to break under certain conditions. It lives between the flywheel and the crankshaft. It has two jobs, (1) protect the engine from serious damage and (2) Align the flywheel and crankshaft precisely.

They often break after the blades have impacted something solid like a curb, tree stump, etc.

The symptoms of a broken shear key vary – no start, poor running, backfiring, weak spark. The repair of the shear key isn’t covered here, but you can check out “Lawn mower shear key replacement” it’s for a walk-behind mower, but the setup is close to identical.

Related Questions

Why does my lawnmower sputter and then die? This commonly happens when the carburetor is dirty, or the gas is bad. Removing and cleaning the carburetor gas bowl will usually fix the problem, but you’ll need to be sure your gas is fresh. Gas older than one month is likely stale.

Is it normal for a new lawnmower to smoke? A healthy mower engine shouldn’t smoke. Blue/white smoke is a sign that your mower is burning oil; this sometimes happens if it’s overfilled with oil. Black smoke means it’s getting too much gas, try cleaning or replacing the air filter.

Hey, I’m John, and I’m a Red Seal Qualified Service Technician with over twenty-five years experience.

I’ve worked on all types of mechanical equipment, from cars to grass machinery, and this site is where I share fluff-free hacks, tips, and insider know-how.

And the best part. it’s free!