Engines often have confusing symbols and indicators that leave users guessing how to properly operate them. One common symbol that generates a lot of questions is the choke symbol on small engines like lawn mowers, trimmers, blowers, generators, and more. This article will clarify what the various choke symbols mean and when to use choke on your outdoor power equipment.
Table of Contents
What Is a Choke on an Engine?
Before diving into the choke symbols, let’s review what the choke does on a small engine. The choke controls the air-fuel mixture entering the carburetor. On cold starts, engines need a richer mixture with more fuel to aid ignition. The choke restricts airflow which richens the mixture.
Once the engine warms up and is running smoothly, the choke should be gradually opened to prevent flooding the engine with excess fuel. The choke symbol reminds users when and how to adjust the choke.
Suggested Video
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What Does the Choke Symbol Look Like?
Choke symbols come in many varieties but generally indicate open and closed positions. Here are some of the most common choke symbols and signs you’ll see:
Closed Choke Symbol
This symbol displays closed air vents indicating the choke is engaged and restricting airflow to enrich the fuel mixture. It is used for cold starts.
Open Choke Symbol
This symbol shows open air vents to represent the choke is open and allowing maximum airflow. Use this position once the engine has warmed up.
Half Choke Symbol
Some engines feature intermediate choke positions, typically half choke. This balanced fuel mixture is used when partially warmed up.
Choke On/Off Symbol
This shows a toggle switch for the choke in both on (closed) and off (open) positions.
Choke and Run Symbol
This displays both closed choke for starting and open choke for running side-by-side.
As you can see, the symbols clearly indicate choke position. Next let’s cover when to use each position.
When Should You Use the Choke on an Engine?
Choke settings depend on the temperature of the engine. Here are the guidelines for properly adjusting the choke:
Cold Engine
Use full choke for cold starts when the engine hasn’t been used recently. This enriches the fuel mixture to aid starting. Avoid prolonged use as it can flood the engine.
Cool Engine
Use half choke if the engine is cool but not completely cold. This provides a balanced air-fuel mix optimal for starting a partially warmed engine.
Warmed Up Engine
An engine that has been running needs no choke. Make sure to gradually open the choke as the engine warms up to prevent flooding with excess fuel. Use the run or open choke position once warm.
Hot Engine
A hot engine also doesn’t require any choke. Opening the choke prevents flooding.
Follow these simple guidelines basing choke position on engine temperature for smooth operation. Refer to the choke symbols to adjust the choke appropriately.
Suggested Video
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Why Use a Choke on Engine Startup?
Using the choke correctly is crucial for starting small engines. But why is the choke so important? Here are key reasons:
Enriches Fuel Mixture
Choking the air intake enriches the air-fuel mix entering the carburetor. The added fuel aids cold starting.
Improves Atomization
The restricted air flow improves fuel atomization from the carb. Better atomization gives a more combustible air-fuel vapor.
Raises Intake Vacuum
Choking increases vacuum in the intake which draws more fuel in, further enriching the mix.
Prevents Lean Stalling
A choke prevents lean stalls from an overly air-rich mix on a cold start.
So in summary, the choke richens the air-fuel ratio to aid cold starting and prevent lean stalls.
What Happens If You Leave the Choke On Too Long?
While the choke is crucial for starting, leaving it on too long can flood the engine and cause stalling. Here’s what happens:
Excessively Rich Mixture
A closed choke gives an extremely rich fuel mixture. Prolonged choking results in an over-rich air-fuel ratio.
Engine Flooding
The rich mixture overwhelms the engine and can’t be fully burned. This floods the combustion chamber with excess raw fuel.
Loading Up and Stalling
Flooding causes loading up with unburned fuel which hampers performance. The engine coughs, sputters, and eventually stalls.
Hard Restarting
Stalling from loading up leaves raw fuel making restarting difficult. The plugs are wet and cylinder flooded.
So prolonged choke use leads to terrible performance and stalling. Make sure to gradually open the choke as the engine warms up. Look for the engine running smoothly as an indicator to slowly reduce choke.
Do All Engines Have a Choke?
While most small engines have chokes, some don’t. Here’s a breakdown:
Carbureted Engines
Carburetors mix air and fuel. so carbureted engines feature chokes to richen mixtures. This includes most lawn mower, trimmer, blower, generator and older motors.
Fuel Injected Engines
Modern fuel injected engines don’t have chokes. Fuel injection electronically adjusts fuel ratios for starting. So chokes aren’t needed.
Electric Start Engines
Some small engines like mowers have electric starters that don’t require choking. These pull enough current spin the motor fast enough to start without choking.
So in summary, carbureted small engines found on most lawn and garden equipment have chokes. More advanced fuel injected or electric start motors often eliminate the need for choking. Check your engine type if unsure whether it has a choke. The presence of a choke symbol indicates the engine is equipped with one.
How Should You Start an Engine With a Choke?
All small engines need a specific starting procedure for smooth operation. Follow these proper steps when starting an engine with a choke:
1. Close the Choke
Engage the choke by closing to the start or closed position. This enriches the mix for starting.
2. Prime the Carburetor
Optionally prime the carb by pushing the bulb 2-3 times. This sends fuel into the carburetor throat.
3. Pull the Starter Cord
Pull the starter cord with short, brisk, straight pulls. Repeat until the engine tries to start or “pops”.
4. Allow the Engine to Warm Up
Let the engine run 15-30 seconds to gradually warm up. Begin slowly opening the choke.
5. Open the Choke
Fully open the choke for unrestricted airflow once the engine runs evenly without sputtering.
This routine ensures fast, reliable starting with the choke helping ignite the cold engine. Make sure to open once warm to prevent engine flooding.
Suggested Video
Here is a video showing the complete starting procedure with a choke:<iframe width=”560″ height=”315″ src=”https://www.youtube.com/embed/E1tASmLf0YM” title=”YouTube video player” frameborder=”0″ allow=”accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share” allowfullscreen></iframe>
Why You Shouldn’t Use the Choke on a Hot Engine?
As outlined before, the choke enriches the fuel mixture to help cold starting. Using the fuel-rich choke on a hot engine can cause major issues:
Creates Extremely Rich Mixture
Hot engines already atomize fuel fully and don’t require extra enrichment. Adding choke makes the mix dangerously rich.
Risk of Engine Fires
The excess fuel overwhelms the engine and can ignite in the manifold or muffler, creating fire hazards.
Flooding and Loading Up
Just like with prolonged choke use, enriched mixtures on hot engines flood the combustion chamber leading to stall out.
Hard Starting
The excess fuel fouls the spark plug and fills the cylinder, making the engine difficult to restart once loaded up.
So in summary, never engage the choke on a hot engine as you risk dangerous backfires along with loading up which requires time to dissipate before restarting.
Do Choke Settings Matter for Engine Performance?
Proper choke settings directly impact engine performance and health. Here are key ways:
Enables Cold Starts
Using full/closed choke allows cold engine starting. Without enriched mixtures, cold starts become nearly impossible.
Prevents Lean Stalling
Choke prevents weak air-fuel ratios allowing smooth acceleration and preventing lean stalls.
Aids Transitions
Adjustable choke eases throttle transitions. Open choke prevents bogging down under throttle changes.
Reduces Wear
Easy starting enabled by correct choking reduces wear related to excessive cranking and labored startup.
So dialing in the right choke settings makes engines start with less effort while running cleanly across the power band for reduced wear. Choke supports performance.
What’s the Difference Between a Choke and Throttle on an Engine?
The choke and throttle both control air intake but have distinct purposes:
Choke
The choke regulates airflow purely to enrich fuel ratio for cold starting. It remains fixed open once running.
Throttle
The throttle controls airflow to regulate engine power output, similar to an accelerator pedal in a car.
So in short, the choke helps starting while the throttle controls power. Confusing these leads to improper operation. Make sure to open the choke once started and use the throttle to vary engine speed.
Conclusion
In summary, choke symbols indicate richer or leaner fuel mixtures from restricted airflow in carbureted small engines. Close the choke when starting cold engines to provide an enriched air-fuel mixture. Make sure to gradually open the choke as the engine warms up to prevent flooding. With proper choke use, engines start easily and accelerate smoothly. Understanding the choke allows proper small engine operation.
Suggested Final Video
For further information, here is one last video summarizing choke function and symbol meanings:
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