Aargh!! A sputtering snowblower is frustrating; when it’s sputtering, it isn’t moving snow efficiently, and moving snow is tough enough without this crap, right? Not to worry, I’m a mechanic, and you are in the right place; very shortly, the sputtering will be a distant memory.
A sputtering snowblower is most commonly associated with an air-to-fuel ratio imbalance. Restoring the fuel ratio solves the problem.
In this post, we’ll cover what sputtering is and what causes it. We’ll cover how to read your spark plug, which is useful when diagnosing air-to-fuel problems, and we’ll include links to various fixes.
What is Sputtering?
Engines need an optimum ratio of air (oxygen) to fuel, known as the Air Fuel Ratio (AFR), to run sweet. When the ratio falls outside its operating window, the engine lets you know pretty quickly.
Mechanics often diagnose by ear, and when diagnosing an engine, they will commonly describe how it runs in one of three ways:
|1 Running lean||Not enough gas||Coughing and hiccupping, erratic idle|
|2 Optimum||14.7 parts oxygen |
to 1 part gas
|3 Running rich||Too much gas||Sputtering and spluttering|
It is important at the outset to describe exactly what I mean by sputtering; if we misunderstand each other, this article will still solve your problem, but it will take longer to get there.
In mechanics parlance, most but not all describe sputtering (some say spluttering) as a spitting action or sound or both. The spitting, in some cases, may be seen as droplets of gas that may also be heard and felt at the carburetor intake opening.
It’s important to note that we are using a single word to describe a condition; it’s important to note also the words we use to describe conditions are often misused or misunderstood.
Either way, even if you and I are not on the same page, we soon will be. A simple plug read will tell you if your engine is running rich or lean.
Typically snowblowers suffer from lean fuel conditions, and that’s just the nature of the cold conditions they work in. Colder air is denser, which messes up the critical Air to Fuel ratio (AFR).
A typical lean running snowblower will be hard to start and will protest by coughing and hiccupping when running until it warms up; this is pretty normal behavior when the temps are super low.
Let’s go ahead a pull your spark plug and read its condition; see the table below.
|Plug Color||Mechanics Description|
When we refer to the plug color, we’re referring to the terminal.
As said, I described sputtering (some say spluttering) as a spitting action that may be seen (in some cases) as spitting droplets of gas and may be heard as a spitting sound from the mouth of the carburetor. This condition is caused by an oversupply of gas which may, in turn, be caused by any one of the following issues.
- Overuse of choke (check out choke use below)
- Choke fault
- Stale gas
- Maladjusted fuel screw – check and adjust
- Float sticking
- Needle valve leaking
- Faulty carburetor
- Faulty spark plug
- Faulty coil
- Ignition switch/wiring issue – check for grounding wire
I describe coughing and hiccupping as a poping type sound that is commonly associated with a lean condition. And a lean may be caused by any one of a list of possible issues, which include:
- Choke not applied (check out choke use below)
- Wrong gas type – E15 is not suitable
- Loose spark plug – check plug is tight
- Wrong spark plug type
- Vacuum leak
- Stuck float
- Fuel blockage
- Faulty gas cap
- Head gasket issue
- Valve issue
I wrote a post about a snowblower with a lean condition. You can check it out here “Snowblower poping noise”
An oily plug is a clue that all may not be well with your engine mechanicals. It’s not a given; something as simple as too much oil can cause plug oiling.
The list of other possible causes includes:
Snowblower Choke Operation
Starting a snowblower in cold weather is always challenging, especially so if the choke and primer bulb isn’t being used efficiently. In this section, we’ll outline what choke is and how to use it correctly.
It’s not just snowblowers that struggle to start in cold weather, all vehicles are challenged, and the reason is simple – cold air has more oxygen in it than warm air. And since gas engines only like to run with 14.7 parts oxygen to 1 part gas, they will have difficulty starting when the oxygen volume increase above 14.7. This is known as a lean condition.
Our cars and trucks use a computer, temperature sensors, airflow meters, and fuel injectors to adjust and maintain the optimum ratio, regardless of the ambient temperature.
Our snowblowers aren’t as sophisticated; the operator must manually add and remove choke as required. Using a choke is important when starting all small engines from cold. But especially so in cold ambient conditions, which is every time you start your snowblower, right? The effect of applying a choke reduces oxygen and restores the ratio closer to 14.7 to 1.
But using too much choke is bad also. As the engine heats up, the effects of the oxygen-dense cold air are reduced, and leaving the choke on has the opposite effect; it adds too much gas and creates a rich condition.
In addition, to choke, you’ll find most snowblowers are fitted with a primer bulb. Pressing the bulb adds a shot of gas directly to the carburetor, which improves cold start performance.
Using choke isn’t art; it’s common sense.
Here’s a quick guide to starting a cold engine in cold weather:
- Fuel tap On
- Ignition On
- Choke-full On
- Press primer bulb three times
- Start engine
- Move choke to 3/4
- Reduce choke progressively as the engine heats
A faulty choke is a very valid reason your snowblower is running rich. In this section, we’ll diagnose and adjust the choke.
Diagnosis – The choke test is as follows:
- Remove the carburetor plastic shields (snow blowers don’t use air filters)
- Set the choke to fully off
- Check the choke plate is fully off (open)
Check out the choke test video here.
Adjust – Most choke systems are operated by a handlebar-mounted choke control lever. When mounted there, they will employ a cable to activate the choke plate at the carburetor. The cable stretches over time and requires a little tweak.
The process is as follows:
- Set the choke to fully off position
- Follow the choke cable to where its mounting bracket at the engine
- Loosen, but don’t remove the bracket
- Now manually (use your fingers) open the choke plate fully and or push the choke cable towards the carburetor a little
- Tighten the choke mounting bracket
- Test your choke
The choke should now move freely from fully On (closed) to fully Off (open) when activated.
When your snowblower sputters, it tells you its air-to-fuel ration is off. Restoring the ratio will fix the issue. Removing and reading the spark plug is the fastest way to tell what’s happening inside your engine.
A wet or black plug means it’s running rich, a white plug means it’s running lean, an oily plug could mean a mechanical issue, and a tan plug means all is normal.
You may find the following pages useful: