Bad Fuel Symptoms
You make your way to the garage or shed, ready to tackle the day’s yard work, only to find that your lawn mower won’t start.
Did you know that bad gas is one of the most frequent causes of small engines not starting? Read on to learn about how to diagnose and treat engines affected with bad gas.
How long can gas be stored before it goes bad?
Whether in a gas can or in your mower, gas can go stale and lose its volatility in as little as 30 days. Using Sta-Bil Storage Fuel Stabilizer can increase storage time up to 24 months. Of course, many factors contribute to how long gas can be stored, including storage location, temperature, condition of the fuel container, and more.
What are the symptoms of bad gas?
If your lawn mower is difficult to start, idles roughly, stalls out, or makes a “pinging” sound, you may have a case of “bad gas”. And no, we’re not talking about the after-effects of dinner at your favorite Mexican restaurant.
How can I tell if the gas has gone bad?
The easiest way to diagnose gas is to smell the fuel in question. Oxidized gas has a sour smell and is much stronger smelling than fresh gas. The other method is to drain a sample from your machine’s fuel tank or your gas can into a clear glass container. If the gas is dark in color, it has more than likely gone bad. See the image below for a comparison between the color of fresh gas (Left) to gas that has oxidized (Right) and should not be used in your equipment.
Note the color of fresh gas (Left) compared to gas that has oxidized (Right)
What should I do if my equipment has bad fuel?
The best solution is to drain the gas from your equipment and replace with fresh gas. Remember to properly dispose of the old fuel.
How can bad gas affect my lawn mower?
If fuel was stored in the unit for an extended period, areas such as fuel lines and the metering needle may have become gummed up from the old fuel mixture. As gas ages, hydrocarbons in the fuel mixture evaporate and the remaining fuel becomes tacky or varnish-like. This can cause deposits and blockages in your equipment’s fuel system. In severe cases, professional cleaning of the carburetor and a possible carburetor rebuild are the only cure for this situation.
To verify this condition, remove the spark plug(s). If you can’t smell fuel in the combustion cylinder or see or smell fuel on the bottom of the spark plug, the fuel passageways are likely obstructed. If the carburetor is clogged, the use of spray carburetor cleaner and pressurized air may clear the obstruction. If this fails, then you should contact an experienced engine service center to have the system professionally and thoroughly cleaned.
Get the Parts and Tools You Need to Maintain Your Equipment Here at MTD Parts!
Spark plug wrench or socket tool (common sizes are 5/8, 3/4 and 13/16)
How to fix a plastic gas tank on a lawnmower, step by step
Most lawnmowers use a gas engine. They make the machine powerful with high endurance. If the tank is empty, you refill and continue. However, sometimes the plastic gas tank that contains the gas may get cracked. It can be hit by something, but the gases released by the fuel weaken the tank’s walls as well. This makes it more vulnerable to a crack over time.
Cracks can result in fuel leakage that can be hazardous. But a plastic gas tank can be fixed reasonably quickly and easily at your home.
How to fix a plastic gas tank on a lawnmower, step by step:
- Step 1: Remove the fuel out of the gas tank
- Step 2: Detach the gas tank from the lawnmower
- Step 3: Locate the crack on the gas tank
- Step 4: Clean the area around the tank
- Step 5: Fill the crack with melted plastic, or use glue or fiberglass
- Step 6: Reattach the fixed tank to the lawnmower
We recommend going through the entire article as all the details to the before-mentioned steps are discussed in more detail underneath.
- 1 Materials Required:
- 2 Step 1. Remove all the fuel out of the gas tank:
- 3 Step 2: Detach the gas tank from the lawnmower:
- 4 Step 3. Locate the crack on the gas tank:
- 5 Step 4. Clean the area around the crack:
- 6 Step 5. Fill the crack:
- 6.1 – Method 1. Melt the area around the crack using a soldering iron:
- 6.2 – Method 2. By melting a small piece of plastic into the crack:
- 6.3 – Method 3. Use glue or fiberglass to fill the crack:
- 8.1 1. How can I tell if there is water in my lawnmower’s gas tank?
- 8.2 2. Why is my lawnmower isn’t getting any gas?
The following materials will be required to assist you in fixing the plastic gas tank efficiently and successfully:
- Soldering iron
- Safety goggles
- Protection gloves
Step 1. Remove all the fuel out of the gas tank:
Step 1. Park the mower at a suitable location: Park the lawnmowers at a place that can deal with some gas spillage. When you remove the gas tank, it is always possible that some of the fuel spill on the ground.
Step 2. Remove the gas: Remove the gas tank’s cap. Empty the gas tank by disconnecting the fuel line. Another method would be to siphoning the gas from the tank. Make sure that that all the gas is entirely removed from the tank.
Step 2: Detach the gas tank from the lawnmower:
Step 1. Remove the gas tank: The gas tank is attached to the lawnmower’s body with some screws. Remove these screws with the help of a screwdriver, and detach the gas tank.
Step 2. Remove the fuel fumes from the tank: The fuel fumes also need to be removed entirely from the gas tank before starting the main procedure. Take an air compressor pipe and blow air inside the gas tank. This shall remove all the fumes from the gas tank.
The gas tank’s cap should remain removed during the entire process of the tank’s fix. This is done to avoid the creation of any internal pressure inside the tank.
Step 3. Locate the crack on the gas tank:
Step 1. Fill the gas tank with some water: In most cases, you will spot the crack easily. But when this is not the case, close the hole at the bottom connected to the fuel line. Fill the gas tank with water, and keep filling the tank until you spot the leakage point. If that does not work, you can try to increase the tank’s pressure with some help from an air compressor. Use some cloth to decrease the air leakage near the fill cap.
Step 2. Mark the leakage point: Mark the area around the leakage point or the crack using a marker.
Step 3. Remove the water from the gas tank: Remove the water you just used to find the crack from the gas tank, and let it dry.
Step 4. Clean the area around the crack:
Step 1. Position the gas tank on a flat surface: Place a wooden plank or something else below the gas tank, and position it in such a way that the crack faces towards you.
Step 2. Polish the crack’s surface: Grab a small piece of sandpaper and polish the crack so that the crack’s surface becomes even and it becomes more visible.
Step 3. Clean the area around the crack: You need to use soldering iron on the area around the crack, so that area must be clean. Clean the area around the crack by putting some rubbing alcohol on a cotton swab.
Step 5. Fill the crack:
There are three possible methods to fill the crack and, thus, fix the gas tank, depending upon the crack’s size and the thickness of the tank’s walls. All methods will be discussed in more detail below.
– Method 1. Melt the area around the crack using a soldering iron:
This method is used when the gas tank is made from thick plastic. Make sure that the plastic can be melted by trying it on a small part first. See if it indeed melts, and when dried, gets its strength back. When this looks ok the step-by-step procedure to use this method is as follows:
Step 1. Switch on the soldering iron: Switch on the soldering iron, and wait until it’s heated. If the soldering iron can be set at different temperatures, start with a low temperature first.
Step 2. Melt a small trench using the soldering iron: Melt a small trench on the crack in such a way that the soldering iron doesn’t go through the tank; instead only melts the surface.
Step 3. Scoop the plastic into the trench: Now, melt some plastic surrounding the trench, and use a small tool to push this melted plastic into the trench and the crack. Keep doing this until the groove is filled with melted plastic completely.
Step 4. Recheck for any leakage: Fill the fixed gas tank with gasoline, and close the tank’s cap. Shake the tank and check if the leakage exists. Let us tell you something; you won’t see any leakage if you have applied this method step by step.
– Method 2. By melting a small piece of plastic into the crack:
This method can be used when your gas tank doesn’t have thick plastic walls. The step-by-step procedure to apply this method is as follows:
Step 1. Cut a tiny piece of plastic: Some gas tanks have additional plastic around the area of screw holes. Using a hacksaw, cut a small piece of plastic from this area. If extra plastic isn’t available on the gas tank, you may cut a tiny piece from any other thing at your home, which isn’t of any use to you.
Step 2. Switch on the soldering iron: Switch on the soldering iron, and wait until it’s heated.
Step 3. Melt the cut piece into the crack: Place the tiny plastic piece you have just cut on to the crack. Now using a soldering iron, melt this piece, and force the melted plastic into the crack. Keep doing this until the crack is filled with melted plastic.
Step 4. Recheck for any leakage: Fill the fixed gas tank with gasoline, and close the tank’s cap. Shake the tank and check if the leakage exists. But we bet that you won’t see any leakage if you have followed the steps mentioned above correctly.
– Method 3. Use glue or fiberglass to fill the crack:
If melting plastic does not work well in your case, you can fill the crack with something else. You can try to use a glue that can cope with gas. Another material would be fiberglass. Clean the environment from the crack well, and use sandpaper to roughen the area. Then use glue or fiberglass to repair the crack.
Step 6. Reattach the fixed gas tank to the lawnmower:
You have now successfully fixed the lawnmower’s plastic gas tank and can fill in the fuel without worrying.
How can I tell if there is water in my lawnmower’s gas tank?
- Left in the rain: The presence of water in the gas tank is one of the main reasons which halts the lawnmower from starting. It may not be only because the lawnmower was left out open in the rain but also because the gas in the tank condenses, thus creating moisture.
- Sudden stall: One of the water-contaminated fuel indications is that the lawnmower suddenly stalls during its operation.
- Smoke from the engine: Another indication is the emittance of a comparatively more significant amount of smoke from the lawnmower’s engine, resulting from low fuel combustion inside the piston chamber.
- Check with a flashlight: A flashlight can also check the presence of water inside the gas tank. Take the lawnmower in a shady area or indoors, and then shine the light on the tank. Water being heavier than fuel, settles at the tank’s bottom and forms tiny bubbles. These bubbles can easily be spotted with the help of light.
- Drain the gas: Such contaminated gas must be drained from the gas tank immediately, as water can corrode the engine and carburetor’s metallic parts. After the drainage of water-contaminated fuel, dry the gas tank completely using compressed air.
- Keep the gas cap closed: It is also advised to keep the gas tank’s cap closed to avoid the entrance of any moisture inside the tank.
Why is my lawnmower isn’t getting any gas?
There might be multiple reasons that stop the supply of fuel to the lawnmower. A few significant causes, along with their solution, are mentioned below:
- Check for cracks: First of all, you need to check the gas tank for any breakage or cracks. The cracks cause fuel leakage, and thus the lawnmower can run out of fuel within minutes. You need to fix the gas tank or buy a new one in this case
- Clogged filter: Another reason that may cause this issue is a clogged filter. There is a filter between the carburetor and the fuel tank, which stops any dirt or debris from entering into the carburetor. This filter may get clogged with time and eliminates the fuel supply to the lawnmower. The filter must be cleaned, in this case, to continue the supply of fuel to the lawnmower
- Closed valve: Some lawnmowers have a valve that stops the fuel supply to the carburetor. It is often turned off at the end of the season or when the lawnmower needs to be repaired. Make sure that this valve is not turned off
- Clean the carburetor: Despite multiple efforts to halt the entrance of dirt into the carburetor, old gasoline can still form a film inside the carburetor, thus stopping its working. A malfunctioned carburetor will stop the supply of fuel to the lawnmower’s engine. You need to open the carburetor and clean it from inside using gasoline and a brush gently.
You don’t need to buy a new gas tank if it’s a little cracked, thanks to the methods mentioned above that can be used to resolve your problem. Gasoline leakage not only drains the fuel faster but can also be hazardous as it is highly flammable. So, it’s advised to get it fixed as soon as possible. Also, don’t forget to wear protective gloves to protect yourself from unnecessary burns and cuts. Safety goggles must also be used to protect your eyes from toxic fumes. All the tools used in the process must be kept out of children’s reach to avoid accidents.
Lawn Mower Storage: Why Draining The Fuel Tank Is A Mistake
Wondering how you can ensure your lawn mower and outdoor power equipment will be ready to roll when the grass turns green?
If you’ve checked your manufacturer’s guide, you’ve probably seen a suggestion to perform some preventive maintenance prior to storage. This is always a good habit to get into. Some manufacturers will also recommend running your equipment dry before putting it away for the winter.
While draining the fuel tank may sound like a good idea, it could harm your engine.
Running a lawn mower dry will make it harder for it to fire right up when it comes time to take it out of storage. This is true of all your outdoor equipment and tools, from mowers and blowers to trimmers and chainsaws.
Lawn equipment relies on three basic elements to work. If you don’t have all three, your engine will not run:
Clean air will always be available if you take time to clean or replace your air filter. And a clean, properly-gapped spark plug usually takes care of the spark.
But fuel? If you don’t maintain components that help properly distribute gas at the right time and in the right amount, your equipment might not perform well. In fact, it may not run at all.
Draining the tank harms your lawn mowers carburetor
Draining the tank harms the “heart” of your equipment. Think of one of the most important organs in your body: your heart. The lawn mower carburetor is, in many ways, your engine’s “heart.” It blends air and fuel and circulates these elements into an engine’s cylinders.
Each time you drain the gas tank, you inadvertently put stress on your equipment’s critical “organ.” Here’s what happens:
- Draining fuel allows oxygen to enter the lawn mower’s carburetor.It’s impossible to get every last drop of gasoline out. When oxygen attacks the small fuel droplets left behind, it causes gum and varnish. If this debris settles in the wrong place, such as a needle valve tip, the carburetor will need cleaning to work properly.
- Where there is air, there is water (damage).Allowing your gas tank to sit empty for long periods leaves a huge area for water vapor to condense. When moisture collects, it can trigger corrosion in the tank, fuel lines, carburetor and cylinders, and can even cause catastrophic engine failure if a big “gulp” is taken into the engine all at once. (If your mechanic says there is “white rust” in the carburetor, this is why.)
- Fuel system plastics and rubbers are designed to live in fuel.These parts can become brittle and crack when exposed to air.
What to do instead: Avoid risks with gas stabilizer.
Manufacturers sometimes recommend draining the tank to winterize a lawn mower because the worst thing you can do is leave old fuel in an engine during long periods of storage.
You may have followed this advice in the past without noticeable issues, but that doesn’t mean you’re in the clear. If draining the tank becomes a yearly habit, there’s a good chance you’re shortening the lifespan of your lawn mower and other tools.
There’s a much easier way to properly store your lawn equipment. To avoid damage, simply use a quality fuel stabilizer and fresh fuel before putting equipment away for the season.
Here’s how to winterize a lawn mower correctly
Step 1: Buy and stabilize fresh fuel for maximum protection. Adding fuel stabilizer to old fuel will stop it from degrading further, but the fuel may already have broken down.
FUEL FILTERS 101
Step 2: Fill your tank 95% full with fresh, stabilized fuel. Leaving a little room prevents the fuel from expanding and spilling in warmer weather, and reduces the risk of water vapor that can condense and contaminate fuel.
Step 3: Run the engine for a couple of minutes. This gets the stabilized fuel into the carburetor and fuel lines.
While you should still consult with your manufacturer for product-specific equipment and engine maintenance tips, these simple steps apply to all engines, big and small. A few minutes on each piece of yard equipment can save hours when the grass starts growing and the season kicks off in spring.
Water in Gas Lawn Mower: How It Happens What to Do
There are lots of reasons that a gas lawn mower might not start up, but without a doubt one of the most common that I hear of is water in the tank. If you don’t know much about small engines, it might not seem like that big of a deal. A little bit of water never hurt anybody, right?! WRONG! Water in a gas mower can be the source of much frustration – no one loves yanking on the starter cord over and over again – until you take steps to address it.
Signs that You Have Water in Your Gas Mower
Water and gas don’t mix. Water is denser and will sink to the bottom of the tank. If you peer into your tank you might see what look like bubbles or “spots” at the bottom; that’s water. And because it’s sitting at the bottom of the tank, it’ll be sucked up into the fuel line before the gas the next time you try to use your mower.
When there’s water in a gas mower, here is what you’ll likely experience:
Lawn Mower Won’t Start
You crank and crank that pull cord, but nothing happens. There are a few potential causes here, but one of them is water in the engine. And if this is the problem, the fact that it’s not starting probably means that there’s a lot of water in there, as no gas is getting through whatsoever.
Splutters into Action Before Cutting Out
This is what will likely happen if your tank doesn’t have quite as much water in it as in the example above. Some fuel is able to get through and allow you to start it up, but it struggles like hell to maintain enough fuel for combustion and cuts out. This is the most common situation I’ve experienced, although the first scenario is quite common on the first start after winter if you forgot to winterize your lawn mower before storing.
It Runs, But Not Well
If your mower is running, but revving up and down the whole time, this could also be an indication that there’s some water in the fuel system. Not enough to stop the engine from running, but it still significantly affects performance.
There you have it. Three potential indicators that there’s water in your gas mower. Whichever you experience, the objective will be the same: Get that water out.
But first, let’s just quickly explain how the water in your gas mower most probably got there in the first place. Then you might be able to avoid history repeating itself in the future.
Water in My Gas Mower: How Did It Get There?
There are two common ways that water gets into your gas lawn mower:
You’re Using Gas Containing Ethanol
You might have heard people say that gas containing ethanol is no good for lawn mowers. This is why. You see ethanol is basically a magnet for water. It draws the moisture out of the air, and then it condenses on the inside of your tank and sinks to the bottom. This is a particularly common occurrence during the winter break if you don’t either drain the old fuel out or you don’t add a fuel stabilizer. And if the tank is half-empty or less, think of all of that air in the tank…
Leaving the Gas Cap Off Your Mower or Storage Can
While you might not have realized the gas you’re using can cause water to accumulate when your mower is sat unused for long periods, this situation is a bit more common sense. You definitely do not want to be leaving the gas cap off your mower or gas canister for prolonged periods. This will also cause condensation and water build-up.
What You Need to Do If You Have Water in a Gas Lawn Mower
You have a couple of options if you determine that the cause of the lawn mower problems you’re experiencing is water.
Remove Your Fuel Tank, Clean It and Fill with Fresh Gas
This option is definitely what I’d personally do. It’s a little more involved, but it’s less risky for the “health” of your mower.
You’re basically going to need to remove the fuel tank from your mower so you can completely drain it, removing all of the old gas that is contaminated with water. You won’t need much to do this:
- Socket wrench (3/8-inch ½-inch socket will usually do the trick)
- Phillips screwdriver
- Flathead screwdriver
Disconnect the spark plug, remove the air filter and then proceed to take out the bolts that are connecting the fuel tank to the mower (there are often 2 on most mowers). Then just wiggle the tank gently from side to side to loosen it, and remove the governor springs (bend them down), and you should then be able to pull the gas tank free.
You can then empty out all of the old gas ( water). I’d recommend disposing of this into a special container that you only use for that purpose. You’re then going to need to remove the primer assembly from the tank, as there’s normally a small pickup reservoir underneath it that could contain some of the contaminated gas. This will be screwed down and there will also be a gasket and a diaphragm (be careful with those) that you’ll need to take off. Then you can clean up the little reservoir I mentioned.
What I do now is take some folded paper towels and push them into the tank to clean up any residue that is still coating the bottom and sides of the tank. You can push this in with a screwdriver so that it reaches all corners of the tank, and then use some pliers to pull it out when you’re ready.
Lawn Mower Repair. Won’t Start After Rain. Water in Fuel
Then it’s just a case of re-attaching everything and adding fresh gas. You should then be good to go!
Option Two: Add Some Isopropyl Alcohol to Your Fuel Tank
I’ve never actually done this, and I’m not sure I’d recommend doing it either. Why? Well because your mower engine likely isn’t designed to burn alcohol and there may be some unexpected “side effects”. Having said that, I have seen folks online mention that they’ve done this when they’ve had a small amount of water in the fuel tank, and it worked. I think that’s the trick though – I definitely wouldn’t try this if you have a lot of water in the tank. You’re much better off removing the tank and following the steps I outlined above in that situation.
You can actually use isopropyl alcohol, methyl alcohol or ethyl alcohol for this. Just make sure you get 99% alcohol content though, as if you get a bottle of 70% you’re just adding more water…You might be wondering how in the hell adding alcohol to the equation is going to help?
So remember we said earlier that gas and water don’t mix. The gas rises above and traps the water beneath it. But alcohol and water DO MIX. And the alcohol WILL BURN, and it’ll take the water with it.
But as I said before, your lawn mower probably isn’t set up to burn alcohol, so do this at your own risk. I always go with tank removal and a thorough clean.
Water in a Gas Mower is Not a Problem that Will Fix Itself
You must take action if your find water in a gas mower, as it can render your mower useless and potentially lead to irreparable damage through corrosion if left long enough.
About Tom Greene
I’ve always had a keen interest in lawn care as long as I can remember. Friends used to call me the lawn mower guru (hence the site name), but I’m anything but. I just enjoy cutting my lawn and spending time outdoors. I also love the well-deserved doughnuts and coffee afterward!
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