A choke lever is a strange concept for many. But for those old enough (1970’s kids), the choke lever is a familiar ritual when starting the family car. I still remember starting my father’s car. Using the choke does require a little finesse. But once you learn how it works, there’s no mystery to it.
A snowblower choke is used to start a cold engine. To correctly start a snowblower using the choke, follow these six steps:
- Set start switch to “On”
- Set gas to “On”
- Set |throttle to “Full”
- Set choke to “On”
- Press primer bulb twice
- Pull start engine
In this post, you’ll learn how to identify choke when and how to use it. You’ll also learn how it works, symptoms, and the danger of excessive choking. In addition, you’ll learn why some snow blowers will only run with choke applied.
How To Identify Choke
The choke control lever on many machines is incorporated in the throttle control. Some manufacturers use the choke symbol to identify the choke, and others may use the word “Choke” on the lever bezel.
It’s not uncommon for the choke lever to be located at the carburetor itself. When it is, the choke symbol may be embossed on the air filter cover to help identify choke “On” and “Off” positions.
The choke symbol represents a choke plate in the closed position. It takes a little imagination. See the picture attached.
More modern and expensive snowblower engines may employ Auto choke and, of course, won’t have a choke lever or symbol since there’s no action needed to apply the choke.
When And How To Use Snowblower Choke
To start a cold snowblower engine successfully, we’ll need to operate the choke. Many snow blowers will warm up after idling the engine for just five minutes or so (ambient temperature-dependent).
It’s essential to allow the engine to warm up before moving to full throttle—engine oil when cold is thicker than when it’s warm. Allowing the oil to warm a little before going to work helps the oil do its job and coat all the components of the engine. Most engine wear occurs because of a lack before and during the warm-up period.
All snowblowers are fitted with a cold start system. A choke plate and a primer bulb are typical. However, some higher-end blowers may be fitted with auto-choke.
Starting a Cold Snowblower Engine
Best to check the oil is when the engine is cold. I advise my customers to check the engine oil every time they fill the gas tank, or at least once a week during the on-season.
Follow these simple steps to start a cold engine:
Set switch to “On.”
Set gas to “On”
Set throttle to full
Set choke lever to “On”
Press primer bulb twice
Pull start engine
As the engine warms up, progressively reduce choke
You’ll know when the warm-up cycle has finished, the engine will run smoothly without a choke. Great job, now that’s how you start and warm up an engine using the choke.
Starting a Hot Snowblower Engine
Starting a hot snowblower engine is usually identical with the exception of the warm-up period. It should be noted that many won’t need any choke at all to start when hot, but depending on how cold the ambient temperatures are you may need to apply some choke to start the engine.
Here’s the process for those snowblowers that need a shot of choke on hot start:
Set throttle to full
Apply ½ choke
Start the engine
Move choke to “Off” position immediately
How Snowblower Choke Works
The choke control is very basic on most snow blowers. Usually, it consists of a lever, cable, and a choke plate within the carburetor. Pulling on the lever tightens the inner cable which in turn closes the choke plate. The choke plate is so-called because when closed it restricts or chokes off the air supply.
Choking off the air supply to an engine that we are trying to start admittingly sounds counterproductive. But there’s no real mystery to it. As you know, cold air is denser than warm air. Meaning a measure of cold air contains far more oxygen than hot. Oxygen and gas are what a carburetor is designed to mix, and it must do so very precisely in order to run smoothly.
The optimum relationship or ratio is 14.7 parts air (oxygen) to one part gas. It’s known as the AFR (Air Fuel Ratio) and your snowblower’s carburetor is calibrated (hot) to mix the air and gas to this ratio.
The problem is when the air and engine are cold the ratio is out of spec. The mix, if you like, contains too much oxygen. Another way to look at it, there’s not enough gas in the mix.
There are two ways to solve this imbalance, reduce the air supply or add more gas. And because snowblowers operate in extreme conditions, manufacturers often fit two methods of rebalancing the air-fuel ratio. Snowblowers are commonly fitted with a choke plate and a primer bulb.
Most small engines are fitted with one or other of the following choke systems, a snowblower is commonly fitted with both a choke plate and primer bulb.
Choke Plate: By far the most common type. Applying the choke plate type actually both restricts air (oxygen) supply and increases gas supply.
It is the most effective choke type however it requires adjustment from time to time.
Primer Bulb: Most snowblowers employ a choke plate and a rubber priming bulb. Pressing the bulb adds extra gas to the carburetor for cold starts.
Auto Choke: A snowblower with auto choke employs the choke plate type, but also a mechanical, thermal switch that senses engine heat and progressively removes choke proportional to warm up.
Symptoms Of Excessive Choke
Excessive choke means, for the most part, forgetting to turn the choke off after the warm-up period. This is a very common occurrence and has some lasting effects on the engine. We’ll talk a little about that in the next section. While operator error is the most common cause of excessive choke, it’s not the only cause.
Other reasons the choke may remain “On” include:
Choke plate binding – clean carburetor
Choke cable maladjustment – adjust cable
Choke lever/cable binding – free cable (WD40) or replace
Check out the choke troubleshooting video here.
The symptoms of excessive choke include the following:
- Engines runs poorly
- Engine sputters
- Air filter wet
- Black smoke from muffler
- Excessive smell of gas
- Engine flooding
- Spark plug fouling
Dangers Of Excessive Choke Use
Running a snowblower with the choke set to the on position won’t do any damage in the short term. However, consistently running the engine with the choke on will have some harmful results.
Running with the choke on or partially on will cause gas to dilute the engine oil. The oil is there, as you know to protect the engine internals from friction. In addition, excessive gas inside the engine washes the layer of protective oil from the cylinder wall.
This usually results in either excessive engine wear or the engine seizes solid. In both cases, it, likely more economical to replace the engine than to repair it. A snowblower that only runs with the choke partially applied is a common complaint. It usually happens at the start of the new season, and the root cause is usually a dirty carburetor.
Grit or debris in the fuel system or carburetor restricts gas flow and as you know that causes an AFR imbalance. Applying the choke helps because it restricts airflow and allows the engine to run smoothly. But while the engine may run smoothly with the choke set to on, it is not running to capacity, and you may find the engine loses power when you enter the snow.
The only solution is to clean the carburetor. Check out the carburetor cleaning video here.