A lawn mower should only act like it is running out of gas when it’s actually running out of gas. If you find there is still gas in the fuel tank, but your lawn mower is showing symptoms of being out of gas, then you’re going to have to stop and grab some tools. There are several potential reasons this could be happening, and it is going to take some figuring out. So, let’s dig in and discover what’s going on.
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Lawn Mower Acts Like it is Running Out of Gas (The Short Explanation)
If a lawn mower acts like it is running out of gas, then it more than likely has an issue with fuel getting to the engine. Defective components within the fuel delivery systems can starve a lawn mower’s engine of fuel and show symptoms similar to the lawn mower having no fuel, or running out of fuel.
The Most Likely Causes of Your Mower Acting Like It’s Running Out of Gas When It’s Not
When a lawn mower acts like it is running out of gas, it basically is. With reduced fuel flow, the lawn mower’s engine will cough and sputter, then eventually stall. This is probably why you think it’s out of gas. Here are the components that could be stopping the fuel from getting to the engine.
- Gas Cap
- Fuel Lines
- Fuel Filter
- Fuel Pump
- Carburetor
Diagnosing the Gas Cap
The gas cap on your lawn mower is probably vented. This means there is a tiny hole in the cap that allows air to enter the tank when fuel is used. If air can’t enter the vent and get into the tank, then a vacuum will form. This vacuum holds the fuel in the tank and makes the engine think it’s out of gas.
So, pop off your gas cap and take a look at the vent. If you see that it is blocked or damaged in some way, then you have to carry out a quick fix.
Inspecting Fuel Lines
Fuel lines are prone to becoming blocked and even degrade over time. Both junk in the tank and fuel through the lines can cause a reduction in the flow of fuel.
So, to check if the lines are causing you an issue, you’ll need to disconnect them and carry out an inspection. Now, this can be done using a few different methods, but I like to completely remove the line to get a good look. A quick note before you get started; if you still have fuel in the mower, it would be best to drain the fuel tank first.
If you take a look in your lawn mower, you’ll find several fuel lines. This can vary on different lawn mowers, but these are the places to look.
- Fuel Tank to Fuel Filter
- Fuel Filter to Fuel Pump
- Fuel Pump to Carburetor
So, take a pair of pliers and remove the clips that secure the fuel lines to the various components. Then, pull or twist off the existing fuel lines. You may want to have a rag close by to mop up any fuel in the lines. Once the fuel lines are off, take a small bottle brush and pass it through the different lines. If there is anything in the lines, you should find it with a bottle brush.
Tools Needed to Inspect Fuel Lines
- Pliers
- Shop Rag
- Bottle Brush
Inspecting the Fuel Filter
If replacing your fuel filter is not already on your lawn mower maintenance checklist, then it would be a good idea to add it. As the name describes, a fuel filter filters out impurities and junk from the fuel to help protect components further down the line. One of the early symptoms that a fuel filter is on its way out is the lawn mower acts like it is running out of gas.
So, if you have a transparent filter, you can look to see if the internal filter membrane is discolored. This discoloration is an indication that the filter has been doing its job. Unfortunately, not all fuel filters are transparent, which I’m sure some of you will find out.
Now, if you know you haven’t changed your filter in some time, then it would be a good idea to change it out and eliminate it from the list of potential causes. You never know; this could actually be the root of the problem.
Testing the Fuel Pump
To test a fuel pump, you’ll be checking to see how fuel flows through it. So, to avoid wasting time, I recommend that you check the lines and filter first, as these components are before the pump. If you have an expired filter or clogged line, you could end up testing the pump unnecessarily and, even worse, replace a perfectly good pump.
So, start by removing the outflow fuel line from the carburetor using a pair of pliers and placing it into some form of fuel-safe container. Next, crank the engine by turning the ignition key or pulling the starter cord. I recommend getting some help on this part so that you can keep an eye on the fuel.
Once the engine cranks over, fuel should flow from the fuel line into the container. The fuel should flow in a steady stream. If the fuel spits out or doesn’t flow at all, then you probably have a bad pump.
Tools Needed to Inspect the Fuel Pump
- Fuel-Safe Container
- Pliers
Inspecting the Carburetor Jet
You would be surprised by all the different symptoms of a bad carburetor. This includes a bad carburetor jet. The carburetor jet is responsible for vaporizing the fuel at a very precise level and jetting fuel into the cylinder head. Small particles and fuel gum can easily build up inside the tiny opening of the jet and restrict the flow of fuel.
This means even the smallest obstruction can cause your lawn mower to act like it’s running out of gas. So, to inspect the carburetor, you’ll need to remove the jet and look for blockages and anything causing an obstruction.
If you take a look at the bottom of the carburetor, you’ll find the fuel bowl. Usually, there will be a bolt in the center of the bowl that can be removed using a socket wrench. So, use your wrench to remove the bolt, then remove the bowl from the carburetor.
Next, use a screwdriver and remove the center screw from within the carb. This screw sits between the opening in the fuel float, right in the center of the carb. Once you remove this screw, the jet should fall from the mower as the screw is used to hold it in place.
The final step is to closely inspect the jet. I find it easiest to hold it up to the light and check to see if there is anything causing the problem.
Tools Needed to Inspect the Carburetor Jet
- Socket Wrench
- Screwdriver
What You Should Do If Your Mower Keeps Acting Like It’s Running Out of Gas
Hopefully, if you have run through these five potential causes why your lawn mower acts like it is running out of gas, you have found the cause. So, let’s take a look at what you can do to fix them.
Fixing the Gas Cap
If you have a pin or a needle, you can clear the vent in a gas cap. Simply take a thin wire, such as a pin, and poke it through the vent. If there is any form of blockage, this method should easily clear it. The hardest part of this fix is diagnosing the problem. It’s so simple that most people miss it.
Finally, if you think the fuel cap is damaged, you’ll want to replace it with a new one. Just be careful if you are planning to buy a universal gas cap from the box store, as not all of them are right for your mower.
Replacing the Fuel Lines
During the diagnosis, you completed half the fix. Now all you need to decide is whether you’re going to clean the old lines or replace your mower’s fuel lines with new ones.
My suggestion is that if you have the parts and time, then just replace the lines. So, grab yourself some new fuel line, making sure that it’s the correct diameter, and cut it to length. You will want to make sure that you make nice clean square cuts so that it fits back on the mower snuggly.
Also, when you are cutting the new fuel line, be sure to take your time when cutting it to length. If you cut it too long, you could end up causing the line to bend which will stop the flow. If you cut it too short, you could end up stretching the line, and it may not even fit.
Swapping Out the Fuel Filter
So, to change the fuel filter, you’ll need a pair of pliers and a replacement filter. Start by removing the clips on either side of the filter, which holds the fuel line on the filter. Next, remove the fuel lines from the filter. A quick twist should help this process.
Next, take the new filter and slide it on the fuel line. Again, a twist of the fuel lines should help. Once the line is back on, take your pliers and reposition the clips. If you have never installed a new filter, you may not be aware it has a particular orientation. Fuel is only designed to flow in one direction. So, check your new filter and look for the arrow showing which way it needs to be installed.
Changing the Fuel Pump
Replacing a fuel pump is actually a very quick and easy job that most people can do. All you need is a set of pliers and a socket wrench.
So, start the fix by removing the connected hose clips using a pair of pliers. Then, twist off the hoses using a similar motion you use to remove the fuel line from the fuel filter. Then, take a socket wrench and remove the bolt that holds the pump to the engine.
Once you remove these bolts, you’ll be able to remove the old pump from the engine. Next, position the new pump on the engine and install the bolts you previously removed. Finally, attach the hoses, being careful to attach them in the same order they were in originally, and reposition the hose clamps.
Cleaning the Carburetor Jet
If you have found that your mower has an obstructed carburetor jet, then you’ll want to use a tool small enough to clear it. I find the easiest way to do this is to use either a small metal file or a pin tool. You just need to be careful not to damage the inside of the jet and avoid making the opening any larger.
So, once you have cleared the blockage, reinstall it back into the carburetor and replace the screw that holds it in place. Then, install the fuel bowl and secure the center bolt.
