Are Lawn Mower Gas Caps Universal? – Tips Guide
When caring for your lawn mower, one of the most important aspects to pay attention to is its gas cap. This part is essential in keeping a consistent fuel flow and avoiding spills that can be hazardous on the grass and other items like patio furniture.
Gas caps get lost often, the reason being that they are vibrated off during use. If this happens, replacing the Cap is essential to keep your lawn mower running correctly and safely.
The question then becomes, are lawn mower gas caps universal? The short answer is no. Mower gas caps are not universal. However, many different models are usually available that are compatible with a wide range of mowers.
Note- It can be confusing to determine whether a new gas cap fits your lawn mower, but thankfully, the critical factor is your engine’s model number rather than the lawn mower itself. Knowing which engine model is in your lawn mower can save you time and money when searching for compatible parts like a gas cap.
In this blog post, we’ll discuss what makes lawnmowers unique, identify the main types of gas caps available today, and provide helpful tips on ensuring your lawnmower responds optimally.
Function Types Of Mower Gas Caps
Gas caps perform mainly three functions, which are as followings:
Two main types of gas caps are available for lawnmowers – the vented Cap and the non-vented Cap. Vented caps are designed with a one-way valve that releases pressure from the fuel tank. This is important as it prevents fuel from backing into the carburettor and fouling the engine. This gas cap is further classified by its material, such as:
Winged Cap – The winged gas cap is generally metal and fitted to the top of the fuel tank. This type of Cap has several tiny wings designed to fit into grooves on the fuel tank, thus creating a secure and leak-proof seal. Although they are not frequently used as plastic threaded caps. These are mainly used for stationary engines, but some mowers still require these gas caps.
Plastic Threaded Cap – Threaded gas caps are plastic and feature a threaded neck that screws into the fuel tank, creating a tight, leak-proof seal. This type of gas cap often comes with an O-ring that helps to create an even stricter seal when screwed in place. They are widely used on lawnmowers and tractors.
Non-vented caps, on the other hand, don’t have this valve feature and are mainly used to prevent fuel from spilling out of the gas tank.
Does a gas tank need to be vented?
For years, tinkerers and DIY-ers alike have used whatever’s available regarding mower caps. That’s why, although a cap is just a cap, when it comes to lawnmowers, the type of Cap can be necessary for engine performance. If your gas cap isn’t vented correctly – as all mower caps need to be – you’ll run into starting problems with your engine.
I’ve seen what happens when an owner reaches for an old oil can cap that fits quite well but is a potential disaster down the line if the Cap isn’t vented. As a mechanic of over two decades, I know how to recognize this situation quickly and help keep engines running optimally by recommending the right Cap for the job.
Often, the landscaper is happy with this repair; however, the engine is not running correctly again after some time. Because the old gas cap was not designed for the specific engine model, it couldn’t ventilate properly, causing fuel build-up in the carburettor.
Punching a hole in the makeshift oil cap would fix the stalling issue. However, this creates a new problem – fuel spills. That’s why it’s essential to always use the correct Gas Cap for your particular lawn mower engine. It is harmful to both environment and a fire hazard.
MacGyver Type Gas Cap
If your covering the gas tank filler neck with plastic is the same problem MacGyver fix that some people try. But, It’s important to note that this is not an actual gas cap and can be dangerous, as it will block off airflow to the fuel tank and create excessive pressure. Additionally, it doesn’t secure the fuel tank or prevent spills.
Common Signs of a bad gas cap include:
- Decrease in engine performance
- The engine stops after thirty minutes of cutting and won’t restart
- Poor fuel economy
- The gas smell from the exhaust
- Engine stalls or stutters when idling
If you want to buy a mower cap, check out the Amazon link below.
What happens if a gas tank is not vented?
With proper ventilation, pressure can build inside the tank, making it easier to fill the fuel tank. Additionally, when a gas tank isn’t vented, fuel vapours can escape, which could be hazardous if they come in contact with an ignition source.
Is there a difference between a gas cap and an oil cap?
Yes, there is a difference. Oil caps are usually made of metal and feature fins that help ensure a tight fit when twist-locked to the top of the oil tank. On the other hand, gas caps typically have a threaded neck that screws into the fuel tank creating a leak-proof seal. They also usually come with an O-ring that helps to create an even tighter seal when screwed in place.
Does fuel need air?
Yes, fuel needs air to combust. Without oxygen in the combustion process, the power will not be able to burn and create energy for the mower engine. This is why it’s essential to use a vented gas cap so that air can enter and exit the tank as needed.
Maintaining a good gas cap is essential for running your lawn mower smoothly. Gas caps help keep the fuel in your gas tank secure and provide a proper venting system for your fuel tank.
Without the correct gas cap, air can enter the fuel tank and create an emulsion that can clog up engine filters and disrupt the air-fuel ratio.
Douglas Mackalie is a Founder of Mackalies Garden. He is one of the most exciting people you’ll ever meet. He has 25 years of experience in horticulture and gardening, most of which he’s spent outdoors getting his hands dirty.
Briggs And Stratton 596250 550Ex Gas Cap Oem
SKU: 596250-A UPC: #N/A MPN: 596250-A Condition: New Availability: Ships (leaves our warehouse) within next business day if in stock Important Notice:
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Briggs and Stratton 550EX Gas Cap
Worry your gardening tool’s engine may leak fuel? The Briggs and Stratton 550EX Gas Cap is the perfect component to prevent that from happening. This is an OEM component you may get from our store at a great price. Get this and other Briggs and Stratton 550EX parts from us now.
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- Poulan Pro PR550N21RH3
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Briggs and Stratton 550EX Gas Cap Specs (596250)
Product number: 596250
Where used: 08P5, 092J, 093J, 09P6, 09P7
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.
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.
Why is My Lawn Mower Gas Cap Leaking?
You’re halfway through your lawnmowing session when you suddenly smell a gasoline smell around the tank and drips of gas leaking from the cap! Just the smell around the tank alone will indicate that your mower’s gas cap is leaking, and you’ll need to shut that off immediately.
If left unattended and untreated, it ends up being dangerous for the rider, the gas, and the mower itself. You wouldn’t want your lawnmower to consume even more gas than it should, which is costly. So you’re probably wondering, why is my lawnmower gas cap leaking?
Read on to find out the possible reasons why!
Why Is My Lawn Mower Gas Cap Leaking?
The gas cap on a fuel tank is a crucial role in the mower’s evaporative emission system. It is a reliable seal, preventing any dust and debris from coming into the gas tank and keeping anything from spilling. But over time, as you refuel your mower, the gas cap would wear out.
You will know if you have a bad gas cap if you notice the following:
This is a common and major symptom of a broken gas cap. It would leak a fuel smell around your lawnmower. A broken gas cap would allow fuel vapor from the gas tank to start leaking from a filler neck.
If you notice this as you mow your lawn, switch off your mower immediately and take it to storage, away from flammables, to repair immediately.
Cap Doesn’t Tighten
Another common sign of a broken gas cap is if the cap itself won’t tighten well. The gas cap would click when it seals air with the filler neck. If ever you don’t hear a click or see it become loose even after the click, then it means it is leaking fuel vapor.
Fuel Cap Venting Test
Another way to find out if you have a broken gas cap is to conduct a short fuel cap venting test. This will show if your fuel cap works well or if it isn’t venting well.
Do this by unleashing your fuel wire, using a container to reserve fuel until your fuel tank is completely empty. Afterward, check if your mower’s tank is empty or not.
If it is, then the fuel flow would gradually become slower. If ever there is fuel left in the tank, then your gas cap isn’t venting properly and you’ll need to repair it.
Problems Behind the Gas Leak
If ever you notice your mower leaking gas, here are the common problems to watch out for:
Worn Out Gasket
If you notice a gas smell around the lawnmower, it may be leaking from the carburetor, which also means your carburetor bowl gasket is worn out.
Broken Float Assembly
The gas cap has a lot of float assemblies operating. Any defects in the float assembly would cause problems, including gas leaks. Float needles, float valves, or even the float itself may end up becoming defective because of the leaking gas.
Leaking Fuel Line
While this isn’t directly related to the problem as to why your lawnmower gas cap is leaking, the consequences are similar and need to be addressed.
Brittle Primer Bulb
The primer bulb is what will draw fuel from the mower’s carburetor when pushed for priming the engine as you start for the first time. Over time, the rubber bulb ends up getting cracked or brittle, causing the bulbs and gas cap to start leaking gas.
There are also other issues to take note of, such as:
- You overfilled the tank with too much gas
- Your vents are dirty and need cleaning
- Loose bolts or mounts
- Unbalanced blades
- Bent crankshaft
- Broken parts
Now that you know why your gas cap leaks, what is the solution? Here are a few tips you can follow:
- Replace the whole gas cap using the original factory parts, which is the instant solution. Just make sure you’re careful when replacing it to prevent extra force, which spoils your air seal.
- Insert a new rubber gasket, which will help make sure that your filler neck has an air-tight seal, preventing any dust and debris from entering the fuel tank while maintaining good venting.
- Use a ziplock bag as a temporary solution until you can have it repaired and replaced. Doing this holds gas in the bag and you shouldn’t use it while mowing the lawn.
- Have it checked by a professional to make sure there aren’t any broken parts in the mower.
Wrapping It Up
After all of what was said above, you might be asking if you can use a mower without fuel caps as a quick solution. While Internet users have said it works, this is NOT recommended at all, as gas would spill as you use the mower. This isn’t only a fire hazard, but unhealthy for your grass and any nearby plants, so have your gas cap fixed right away.
I hope that you learned a lot about why your lawnmower gas cap is leaking and what to do about it. If ever your lawnmower seems to have a leaking gas cap, it’s time to have it fixed right away after identifying the issue. Good luck!