A carburetor blends air and fuel using nothing but airflow and vacuum, no electronics required. It was the standard fuel delivery device before fuel injection took over.
Animated: how a Carburetor actually works
🔧 How It Works, Step by Step
1
Air rushes through the venturi
Incoming air accelerates through a narrowed passage called the venturi, which lowers pressure.
2
Low pressure draws fuel
The pressure drop pulls fuel from the float bowl through metering jets into the airstream.
3
Fuel atomizes with air
The fuel breaks into a fine mist and mixes with the incoming air.
4
Throttle plate controls flow
The throttle plate below the venturi regulates how much air-fuel mixture reaches the engine.
5
Circuits handle different needs
Separate idle, main, and accelerator pump circuits supply the right mixture for each condition.
🧩 The Key Parts
Venturi
Narrows airflow to create the vacuum that draws fuel.
Float bowl
Stores a ready supply of fuel at a set level.
Metering jets
Control how much fuel enters the airstream.
Accelerator pump
Squirts extra fuel for quick throttle response.
Choke
Enriches the mixture for cold starts.
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🩺 Signs of a Failing Carburetor
Hard starting, especially when cold
Rough idle or stalling
Hesitation or bog on acceleration
Fuel odor or flooding
Black smoke from a rich mixture
⚠️ Common Problems
Clogged jets
Fuel varnish blocks the tiny jets, upsetting the mixture and causing rough running.
Float issues
A stuck or sunk float sets the wrong fuel level, causing flooding or starvation.
Worn accelerator pump
A failed pump diaphragm causes a hesitation or bog when you open the throttle.
💰 Cost to Fix
$150-$600typical range to repair or replace, parts and labor
❓ FAQ
Why did fuel injection replace carburetors?
Injection meters fuel far more precisely across all conditions, improving economy, emissions, and cold starting compared to a mechanical carburetor.
Do carburetors need tuning?
Yes, carburetors require periodic adjustment of idle mixture, float level, and jetting, especially with altitude or temperature changes.
What does the choke do on a carburetor?
The choke restricts airflow to richen the mixture for cold starts, then opens as the engine warms.
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