So what causes snowblower backfires? I cover the seven most common issues that cause backfiring and talk about the solutions.
But before that, if you’re having problems starting your snowblower and want some tips on the cause then head over and take a look at my extensive guide on snowblower troubleshooting first.
But for now, let’s get on to why your snowblower is backfiring.
What Is A Backfire & What Causes It?
Chances are that if you are asking yourself ‘why is my snow blower backfiring’, then you have some other problems. This may be that your snowblower surges or that the snowblower will only run on choke.
When any small engine backfires and the problem is not solved it can actually damage the inlet valve and exhaust valve or worse. An engine backfire is caused when there is unburnt fuel in the exhaust system, this fuel then combusts or explodes. If a loud backfire occurs you may even see a flash of flames as the unspent fuel ignites.
Maintaining the correct engine performance requires regular maintenance, but even the best-maintained snow blowers can develop running problems.
What Is Surging & What Causes It?
Surging is when an engine periodically drops revs and then picks up again. This erratic behavior is also referred to as hunting, and trust me it is extremely frustrating. However, don’t worry, it is not necessarily going to hit your pocket.
This can be a simple fix, I’ll talk about this in a bit, so don’t go running to your nearest small engine mechanic. There are a few things that can cause a small engine to backfire or to surge and hunt, the two main culprits are too much airflow and not enough gas, or spark plug problems.
So, let me get to the point, solutions for a snowblower backfiring and/or surging.
How To Fix A Snowblower Backfiring Or Surging
Fixing the problem of a backfiring snowblower or in fact, any small engines including your lawnmower needn’t cost you money. When you have the know-how and don’t mind attempting a little DIY mechanics it is a lot simpler than you think.
Here I take a look at all the main causes and the solutions to them.
1. Is Your Snowblower Choke On?
Are you having to run your snowblower with choke all the time? If you are then you have a problem, the choke should only ever be used when cold starting your snowblower. If you are having to run on choke then pop over and check out my blog on troubleshooting and fixes for a snowblower only running on full choke.
When you run the snowblower with the choke ON you are likely to not only have excessive fuel consumption but irregular engine power, i.e hunting and surging. One of the following problems may be the cause, so read on.
2. Check Your Carb Air To Fuel Ratio: Is It Running Too Lean?
It is really important to know about your snowblowers’ carburetor adjustment as this sets the engine for optimum performance. If the carburetor adjustment is wrong it can mean that your machine is running lean.
This is actually one of the main causes of engine backfire and surge problems. This can also cause you to run on choke as mentioned above.
When you are adjusting the carburetor your aim is to achieve a nice regular idle by altering the mixture of air to fuel ratio. You will need to do this while the snowblower is running.
- Locate the carburetor adjuster, check the operator’s manual if unsure where this is. Usually, this is a small screw, mark or make a mental note of its current position before adjusting.
- With a small screwdriver, you need to slowly turn in tiny, and I do mean TINY, increments. Either left or right. If the idle gets worse instead of better then return the screw to the original position.
- If the first direction didn’t work carry out step two in the opposite direction, this should help.
- If adjusting the mixture has not worked, you likely have a different issue causing your surging, so please read on.
3. Check Your Spark Plug/s
When a snowblower runs unreliably it is very often due to a poor spark, either because of an improperly set gap or sooting. First, check that the spark plug cable and boot have a good fit and are in good condition so that a spark occurs.
Secondly, after running, but when cool, check to see if the spark plug is wet, this will mean that fuel is making it into the combustion chamber ok. If it is dry you likely have a problem with the fuel system.
If it looks grimy or sooty you can just clean off and after making sure that the spark plug opening/gap is set correctly (check your owner manual to find the correct setting) the put it back into place.
If you have any doubts about the condition of your spark plug I recommend that you just buy a new plug. Truth be told, I recommend you replace your spark plug after every season considering the low cost of doing so.
4. Check Your Fuel Lines
In some fuel systems, you will find a fuel filter in the gas line. Check that the filter is clear of debris and gum, they can’t really be cleaned so you will need to replace it if blocked.
After the filter, check that the fuel line is also clear of any debris by disconnecting it from the carb and letting gas run into a container. If the gas runs freely, no problem, if the gas is not running then gently thread a piece of wire through the line until it reaches the gas tank. (You may need to remove a filter to do this).
Note: Always do this in a well-ventilated area and well away from any naked flames, such as pilot lights, etc.
5. Try Using A Fuel Stabilizer
A lot of gas used today contains ethanol, this is not good for any small engines, this includes the snowblower fuel system. So I start by saying always try to use ethanol-free fuel or add a fuel stabilizer such as Sta-Bil.
A fuel stabilizer is a mixture that helps reduce evaporation and water mixing with the gas and is made up of antioxidants and lubricants. When your gas tank is low, add more fuel that has a stabilizer added and then run the engine. Doing this will sometimes clear small amounts of gum from fuel lines and the carb.
6. Drain Your Fuel & Use Fresh Gas
Gas actually has a very short shelf life and can start to go bad after just a couple of months. A fuel stabilizer is used to stop this from happening and help keep fuel tanks clean. It is important that you always read the instructions on the stabilizer carefully as they do vary.
Draining your fuel and replacing it with new gas is especially important if you have not been using a stabilizer or if the snow blower has sat for a long period of time. There are several ways that you can drain your gas:
- Run the snowblower until it runs dry
- Disconnect the fuel pipe from the carburetor and let the gas drain into a container
- Syphon the gas using a fuel siphon pump
Check out my guide with full step-by-step instructions on how to drain gas from a snow blower if you have any doubts.
7. Make Sure Your Carb Is Clean
A dirty carb can affect a small engine and cause backfiring or surging. In this short step-by-step guide, I explain the basic steps involved in cleaning a small snow blower carb.
Initially, you can try using a carb cleaner without removing the whole carburetor. So, if you are happy to get your hands dirty with a little DIY mechanics then here’s what you can do.
NOTE: Always do this in a well-ventilated area and ensure there are no naked flames as there will be a certain amount of fuel leakage from the carburetor. In addition to that, it is important to wear appropriate clothing and disposable gloves and have clean rags or paper towels to hand.
- Locate the carburetor bowl on your machine, tilting the snowblower to avoid the float coming out.
- Undo the bolt on the bottom of the bowl and remove. This will bring with it the main jet.
- Now remove the carb bowl itself.
- Clean out the valve, a thin piece of copper wire is great as copper is softer than brass it will not scratch the precision machining of the inside.
- Clean the bowl thoroughly and remove any residue or gum.
- Reassemble and you should be good to go.
If this has not cured the problem then you may need to fully remove the carburetor and clean or replace it. Check out my more detailed step-by-step guide for cleaning a snowblower carburetor.
Final Thoughts & Wrapping Up
Well, I hope you have found this article useful. Remember regular maintenance and storing your snowblower correctly during the warm summer months will prevent a lot of problems from occurring.
Also, try to use ethanol-free fuel and add a fuel stabilizer to the fuel before refilling your snowblower.
People Also Ask (FAQ)
Here I thought it would be helpful to answer a few more questions that you may be interested in. Hope it helps. Have a safe winter and enjoy the snow.
How do you start a snowblower that has been sitting?
Starting a snowblower should be easy if it has been maintained and stored correctly. In fact, you need to do nothing different.
However, if you have problems I recommend that the first thing you do is drain the fuel. Once drained replace with new gas that has a fuel stabilizer, it’s also worth checking that the spark plug is in good condition.
Where do you spray starter fluid on a snowblower?
Often used for small engines with a carburetor rather than fuel injection starter fuel can be sprayed near the air intake, or into the spark plug hole (this will get fuel into the combustion chamber faster).
How can you tell if an ignition coil is bad?
Having problems starting your snowblower, it is hunting and surging, or it won’t’ idle properly are all signs that can mean your ignition coil is bad. But it could also be the spark plug, using a tester is a cheap and the best way to diagnose a problem.
Can you over prime a snowblower?
You can quite easily over prime a snowblower engine by pressing the primer too much. This will result in the opposite of what you are trying to achieve.
It will flood the carburetor and the engine will not start, turn the choke OFF to allow more air than fuel in. Now try to start it with the pull cord or electric start a few times, this should ‘unflood’ the engine.