If your lawn mower ran out of gas and won’t start, there could be a few reasons. Generally, the problem is either related to your spark plug, fuel line, or carburetor. In this article, we’ll discuss why a mower might run out of gas and not start and how to troubleshoot the issue.
I’m familiar with running out of gas while mowing the lawn, as these machines don’t have a fuel gauge. But if you’ve refueled your mower and it still won’t start, you may be concerned about what could have gone wrong. Read more to learn how to troubleshoot a lawn mower that won’t start after running out of gas.
Why Gas Ran Out and Won’t Start?
The most likely cause of a no-start mower after running out of gas is dirt in the carburetor, but other possible reasons include:
- Air-locked gas system
- Faulty carburetor
- Contaminated gas
- Faulty auto choke
- Faulty coil
- Faulty spark plug
Common Problem: Mower Ran out of gas Won’t start – Troubleshooting
As you know, dirt in the carburetor is the most likely cause of the no-start. No, it’s not a coincidence that it happens simultaneously as the gas tank runs flat.
As you’ve probably guessed, it is a result of the mower sucking the bottom of the gas tank, and that’s where all the crap lives. Your mower should have a gas filter fitted, but they don’t catch everything. Besides, the sediment in the bottom of the tank is usually so delicate it has no problem passing through the fuel filter.
Solution- The fix is to clean the carburetor. Some carburetors are easier to work on than others. So just before pulling the carburetor apart, we can try a quick fix – Draining the bowl.
This is a simple job and will very often fix the problem. (more on that below)
Air-locked Gas System
If draining the carburetor bowl has not fixed the out-of-gas issue, we look at air-locking. This occurs when fuel can’t reach the engine because of a blockage between the tank and the carburetor. This usually happens when you leave your mower unused for a while, and it evaporates from the carburetor.
Solution- The fix is to ensure fuel runs freely from the tank to the carburetor. The best way to do this is to disconnect and clean the gas line, then reconnect it and ensure there are no blockages or air-locks. If your mower has a primer bulb, try priming it, too, as this will help to get fuel to the carburetor.
- Dry gas tank – A dry gas tank is also susceptible to air-locking. When the fuel lines run out of gas, they are replaced with air. Adding more gas to the tank pushes the air toward the carburetor, but if the tank isn’t filled up all the way, there won’t be enough pressure to expel all of the air. This trapped air will prevent fuel from reaching the engine. To fix this issue, you can tap on the gas bowl to release any trapped air before opening up the carburetor bowl drain.
- Tap – After replenishing the fuel tank, tap on the gas bowl with a screwdriver or hammer to remove any trapped air. This should help expel any air that’s been blocking the flow of fuel to the engine.
You may need a new carburetor if all other checks and fixes have failed. This is usually quite expensive, so it should only be considered if cleaning the carburetor has not fixed the issue.
There is no connection between a mower running out of gas and a sticking auto choke. Such an issue can be intermittent, or it could be consistent. To check if the choke is working correctly, the air filter must be removed when the mower is hot; at this point, the choke plate should not be closed.
Carburetor Bowl Drain
Draining the carburetor’s fuel bowl is a straightforward job. Many car manufacturers include a specific drain bolt, making the process effortless. The fuel bowl is situated behind the air filter and connected to the bottom of the carburetor. This component serves as a reservoir for storing enough gas to power the engine.
Solution- The fuel system can become blocked up with dirt and air, but often simply draining the bowl for a few seconds is enough to clear out the debris. This process should not replace a complete carburetor cleaning. However, it can relieve minor blockages. If you have issues with your engine’s performance and suspect obstruction in the fuel system, draining the bowl is an easy and quick way to alleviate the problem.
- Carburetor bowl drain bolt – This model features a drain bolt, meaning that removing the bowl is unnecessary to allow gasoline to pass through the carburetor. When the bowl drain is open, fuel should be able to flow freely; if it doesn’t, inspect the needle seat and fuel filter for any blockages.
- Carburetor bowl removal – This B&S engine is quite common. To drain the bowl, it must first be removed. It’s also essential to clean the fuel feed bolt; this is a frequent source of difficulty with starting engines like this one.
It’s worth taking the time to check your gas before filling up your mower. Making the mistake of mistakenly putting something other than fuel into the tank can bring you in trouble. This simple error is widespread when pulling out old gas cans from last season.
Gas only stays fresh for about a month; after that, it can mess with the running of your small engine. If you suspect the gas is causing a problem, go ahead and drain it out and fill it up with some fresh fuel instead. If that doesn’t work, you may need to empty the gas bowl.
Solution- To avoid this problem in the future, buy less gasoline or use a gas stabilizer in the can; this will keep the fuel fresh for up to two years and help protect the fuel systems of all your small engine equipment, including a two-stroke kit.
Faulty Auto Choke
Auto choke, also known as Ready Start by Briggs and Stratton, is a common feature of modern lawnmowers. While it’s generally quite reliable, sometimes the auto choke system can become stuck in the on position, which then causes engine flooding. This issue needs to be addressed promptly for optimal performance.
Solution- The fix is to reset the choke manually. This can usually be done by turning a screw near the carburetor or simply re-seating the linkage if your mower has one.
Consult your owner’s manual for further information on resetting the auto choke system.
The last component we want to discuss is the coil or armature. This plays an essential role in igniting the gas within the engine by creating a spark. Without this crucial element, the combustion process would not be possible.
Coils are a critical component but can quickly fail. If this happens, you may notice intermittent hot start problems. Though these symptoms are unrelated to running out of gas, they’re still worth mentioning at the end of our list.
Solution- If you suspect the coil is faulty, it should be removed and tested. The results of such a test should help you decide if you need to replace the component.
Faulty Spark Plug
Another potential cause of hot start issues is a faulty spark plug. This component can wear out over time due to continued use, leading to the engine not firing correctly when you attempt to start it up. Replacing the spark plug should solve the problem if this is the case.
Solution- It’s worth noting that spark plugs typically need to be changed every few months, and they should always be of the correct grade for your mower. Always check your manufacturer’s manual for the right spark plug type and gap settings.
The lawn mower won’t start after running out of gas? Various issues can cause hot start problems, but running out of gas is the most common. Other potential causes include blockages in the fuel system, faulty carburetors, contaminated gas, faulty auto choke and coils, and faulty spark plugs.
To address these issues correctly, it’s essential to understand what each component does and how they all work together to power the engine. Doing this will help you diagnose and solve the problem quickly and effectively, saving you money and stress in the long run.
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.