You’re standing in your driveway, it’s 20 degrees out, and your snowblower refuses to catch. You look down at that little plastic lever. There’s a weird diagonal line over a circle, or maybe a drawing of a butterfly valve, or just the words "Run" and "Choke" with arrows that don't seem to point anywhere specific. You flip it. Nothing. You flip it back. A sputter, then silence. Honestly, the choke on off symbol is one of the most poorly communicated pieces of user interface in the history of mechanical engineering. It’s a tiny icon that carries the weight of your entire Saturday afternoon.
If you've ever felt like a fool staring at a lawnmower, don't worry. Even seasoned mechanics sometimes have to double-check which way is which on a new model. The reality is that "Choke" isn't just a setting; it's a physical state of the engine's carburetor. Understanding what that symbol is actually telling you to do with the air and fuel mix is the only way to stop yanking that starter cord until your arm falls off.
The Visual Chaos of the Choke On Off Symbol
Manufacturers can't seem to agree on a universal language. On a Briggs & Stratton engine, you might see a circle with a diagonal line through it. To a modern tech user, that looks like "No" or "Cancel." But in the world of small engines, that diagonal line often represents the butterfly valve inside the carburetor being closed. When that valve is closed, you are "choking" the engine.
Then you have the "Run" symbol. This is usually just an open circle. It looks like a zero. Or an "O." It’s meant to symbolize that the airway is wide open and the engine is ready to breathe normally. But if you’re looking at a lever that slides between these two, which side is "On"?
It gets weirder with iconography. Some brands, like Husqvarna or Stihl, use a slanted line that looks like a tilted gate. This is actually a more accurate representation of the internal hardware, but unless you’ve taken a small engine repair class, it looks like abstract art. You’ve basically got a 50/50 shot of getting it right, and getting it wrong usually means a flooded engine and a very frustrated person standing in a pile of grass clippings.
Why We Still Need a Manual Choke Anyway
You’d think in 2026 we’d have moved past this. Most of our cars haven't had a manual choke since the early 1980s. Your Honda Civic manages its own air-fuel ratio using sensors and an ECU (Engine Control Unit). But your weed whacker? It’s a primitive beast.
Engines need a "richer" mixture of fuel to start when they are cold. Gasoline doesn't vaporize well in a cold manifold. By "choking" the engine—literally restricting the amount of air entering the carburetor—you create a high-vacuum environment that pulls more liquid fuel into the combustion chamber. Once the metal warms up and the fuel starts vaporizing more easily, you "open" the choke (the "Off" position) to let the engine breathe. If you leave the choke "On" once the engine is warm, it will stumble, blow black smoke, and eventually die because it’s "drowning" in fuel.
Spotting the Differences: Symbols You’ll Actually See
Let's look at the three most common versions of the choke on off symbol you'll encounter in the wild.
First, there's the Butterfly Icon. This looks like a vertical line with two little wings. If the wings are flat against the line, the choke is closed (On). If they are angled away, it's open (Off).
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Second is the Text/Arrow Combo. This is the most "user-friendly" but still fails often. It might say "Choke" on one side and "Run" on the other. But does the arrow mean "Move the lever this way to Choke" or "This is the Choke side"? Usually, you move the lever toward the word of the state you want the engine to be in.
Third is the Diagonal Slash. This is the one that causes the most grief.
- Slash through the circle: Choke is ON (Air is blocked).
- Empty circle: Choke is OFF (Air is flowing).
The "Flooded" Nightmare
We’ve all done it. You leave the choke on too long, or you try to start a warm engine with the choke engaged. Suddenly, the spark plug is soaked in gasoline. The engine won't fire. You smell gas. You keep pulling.
This is the "flooded" state. When this happens, the choke on off symbol becomes your best friend and your worst enemy. To fix a flooded engine, you actually need to turn the choke completely OFF (the open circle symbol) and hold the throttle wide open while pulling the cord. This forces the maximum amount of air through the system to clear out the excess liquid fuel.
Real World Nuance: The Half-Choke
Not every engine is binary. Some engines, particularly older ones or those running on ethanol-blended fuels that have sat too long, require a "half-choke" position. This isn't usually marked by a symbol. It’s a "feel" thing. You move the lever halfway between the closed slash and the open circle. It’s the sweet spot where the engine stays running while it’s still "waking up."
How to Never Mess This Up Again
The easiest way to master the choke on off symbol is to visualize what's happening inside the tube.
Think of the choke lever as a door.
When you want to start a cold engine, you close the door to keep the air out and the fuel in.
Once the engine "pops" or starts running, you open the door to let it breathe.
If you are looking at a symbol and aren't sure:
- Look at the air filter. The choke lever is almost always physically located right next to where the air enters the engine.
- Observe the movement. If you move the lever and it blocks the hole going into the engine, that is the "Choke On" position.
- Listen. A "Choked" engine has a low, muffled, guttural sound. An "Unchoked" engine has a crisp, higher-pitched roar.
Actionable Steps for a Perfect Start
Stop guessing and start following a mechanical rhythm. It works better than luck.
- Check the Fuel First: Before even touching the choke, make sure your fuel is fresh. In 2026, ethanol-free gas is still the gold standard for small engines. If your gas is more than 30 days old, it’s probably lost its "fire."
- The Cold Start Sequence: Flip the lever to the "Choke On" symbol (the slash through the circle). Give it 2-3 pulls. If it "coughs" but doesn't stay running, move the lever to the middle or "Off" (the open circle) immediately and pull again.
- The Warm Start Rule: If you just turned the machine off five minutes ago to grab a glass of water, do not use the choke. Move it straight to the "Off" or "Run" symbol. The engine is already warm enough to vaporize fuel.
- Maintenance over Luck: If you find you have to keep the choke partially "On" just to keep the engine running while you work, your carburetor is dirty. The choke is compensating for a clogged internal jet. It’s time to spray some carb cleaner or replace the unit.
Knowing your choke on off symbol isn't just about starting a tool; it's about understanding the basic physics of internal combustion. Once you stop seeing a random icon and start seeing an air valve, you'll never struggle with a pull-start again. Go check your mower right now and trace the lever movement to the intake—you'll see exactly what I mean.