The universal choke on and off symbol on portable generators and small engines uses a circle with a diagonal or horizontal line to indicate 'Choke ON' (closed plate, rich mixture for cold starts) and an open circle or vertical line for 'Choke OFF' (open plate, normal air for running). However, confusion frequently arises because 'Choke ON' mechanically means the airway is closed, and many operators mistake the fuel valve symbol for the choke. Below is the complete reference table to decode these panel markings safely and get your equipment running without flooding the carburetor.
Standard Choke and Fuel Control Symbol Reference
Before pulling the starter cord or pressing the electric start button, you must correctly set the air-fuel mixture. The following table details the exact graphical symbols stamped into the plastic or metal control panels of modern portable generators, engine-driven welders, and pressure washers. These symbols are derived from small engine manufacturing standards and are critical for proper cold-start procedures.
| Symbol Name | Visual Graphic Description | Mechanical State | Engine Action | Typical Application |
|---|---|---|---|---|
| Choke ON (Closed) | Circle with a solid diagonal or horizontal line through the center | Butterfly valve fully closed across the carburetor throat | Restricts air, creates high vacuum to pull rich fuel mixture | Cold engine starting (ambient temp below 60°F / 15°C) |
| Choke OFF (Open) | Open hollow circle, or circle with a vertical line parallel to flow | Butterfly valve fully open, parallel to airflow | Unrestricted air, standard stoichiometric air-fuel ratio | Normal running operation, warm engine restarting |
| Half-Choke (Intermediate) | Circle with a partial bar, or a line at a 45-degree angle | Butterfly valve partially closed (approx. 45 degrees) | Moderate air restriction, slightly rich mixture | Warm-up phase, or starting in mild weather (60°F-80°F) |
| Fuel Valve ON | Circle with a solid dot in the center, or vertical line aligned with hose | Petcock or solenoid open, allowing gravity-fed fuel flow | Supplies gasoline from the tank to the carburetor float bowl | Pre-start preparation; must be ON before choking |
| Fuel Valve OFF | Circle with a horizontal line perpendicular to the fuel hose direction | Petcock closed, blocking fuel flow to the carburetor | Starves the carburetor to prevent flooding during transport | Equipment storage, transport, or maintenance |
Regional Standards: ISO 7000 vs. ANSI B71.4 vs. Legacy Markings
While the symbols above represent the modern consensus, the exact graphical implementation depends on the regulatory standard your region and equipment manufacturer follow. Understanding these variations prevents misinterpretation when operating imported or legacy machinery on a jobsite.
ISO 7000 (International Standard)
The ISO 7000 standard for graphical symbols on equipment heavily favors the butterfly valve iconography. Under ISO guidelines, the choke is represented as a cross-section of a pipe with a flap. A line perpendicular to the pipe indicates 'Choke ON' (closed), while a line parallel to the pipe indicates 'Choke OFF' (open). This is the standard you will find on most European-manufactured generators (like Pramac or SDMO) and globally distributed models from Yamaha and Honda.
ANSI B71.4 (North American Consumer Equipment)
In the United States, the ANSI B71.4 standard for consumer turf and power equipment allows for more simplified iconography and heavily permits text-based labels. Many North American-market generators (such as Champion, DuroMax, and Westinghouse) bypass complex circular symbols entirely, opting instead for stamped words: 'CLOSED / START' for Choke ON, and 'OPEN / RUN' for Choke OFF. When symbols are used, ANSI permits the simplified 'circle with a slash' motif, which closely mirrors the ISO standard but often lacks the pipe cross-section context.
Legacy and Old UK Markings
Older equipment, particularly pre-2000s British and Commonwealth small engines, often relied on color-coding rather than stamped symbols. A red lever typically indicated the choke control, while a black lever indicated the fuel petcock. If you are operating a vintage generator or an old engine-driven welder like an early Miller Bobcat, do not look for ISO circles; look for the colored levers and trace the physical cable routing to confirm their function.
Rows People Get Wrong and Faded Panel Troubleshooting
Misinterpreting the choke on and off symbol is the leading cause of flooded carburetors and failed starts on the jobsite. Here are the specific points of failure and how to resolve them when the panel markings are compromised.
The 'ON = CLOSED' Mechanical Paradox
The most common mistake hobbyists and trade students make is assuming 'Choke ON' means opening the choke plate. In electrical terms, turning a valve 'ON' opens it. In small engine mechanical terms, engaging the choke ('Choke ON') closes the airway to restrict airflow. If your generator panel uses the ISO circle-with-a-line symbol, remember that the line represents the physical brass plate blocking the air. Line across the circle = airway blocked = Choke ON.
Confusing the Fuel Valve with the Choke
Look closely at the 'Fuel Valve ON' row in the reference table. The symbol for fuel flow (a circle with a dot or a vertical line) looks remarkably similar to the Choke OFF symbol (an open circle or vertical line). If you accidentally turn the fuel valve OFF while thinking you are setting the Choke OFF, the engine will start, run for 30 seconds on the residual fuel in the float bowl, and then die. Always verify you are interacting with the lever connected to the carburetor intake, not the lever connected to the fuel tank petcock.
Safe Interpretation When Markings are Faded or Missing
Jobsite generators endure UV exposure, fuel spills, and abrasion, which frequently wipe out stamped panel symbols. If your choke lever is completely blank, use this physical verification protocol:
- Trace the Bowden Cable: Follow the metal sleeve and inner wire from the lever to the carburetor. The lever that pulls a cable directly into the side of the carburetor body is the choke. The lever that sits directly under the fuel tank with a short, rigid linkage is the fuel petcock.
- Visual Carburetor Check: Remove the air filter housing. Look directly down the throat of the carburetor. Move the suspect lever. If you see a brass or aluminum butterfly plate rotating to block the circular throat, you have found the choke.
- Map the Detents: Many modern inverters, like the Yamaha EF2000iS, use a sliding lever with physical detents (clicks). Push the lever all the way in the direction that closes the brass plate you verified in step 2. Mark this position with a silver paint pen as 'START / CHOKE ON'. Pull it back one click for 'HALF / WARM UP', and pull it fully back to mark 'RUN / CHOKE OFF'.
For deeper safety and operational guidelines regarding portable power equipment, always consult the CPSC generator safety resources and your specific manufacturer's manual, such as the Honda Power Equipment documentation library, which provides exact symbol legends for their EU and EB series inverter generators.
