Vehicles are now manufactured using a fuel injection system in order to provide the engine with the proper fuel-air mixture. Prior to the 1980s, however, carburetors performed this task. The carburetor is similar to a throttle body in that it contains a pipe and a valve, however a carburetor doesn’t use any electronic mechanisms like a fuel injection system does. Rather it uses the Venturi principle of vacuum creation to allow just the right amount of fuel through a needle valve inside the unit and out to the engine.
At some point the carburetor may become warped, cracked, or otherwise malfunction, and will need to be replaced. People also sometimes upgrade the carburetor for performance purposes.
How to tell if your carburetor is bad
- Hard starts – you may need to hold the key in the start position for several seconds
- Roaring, vibrating, or rough running when idling
- Decreased fuel economy
- Stalling or rough running while driving
- Leaking fuel
This combination of signs doesn’t necessarily mean that the carburetor is bad, but you should have it inspected by a mechanic if you’re experiencing these problems.
Once it has been determined that you need a new carburetor, you’ll need to decide between buying a rebuilt or new one. Carburetors can be remanufactured but it’s critical that you know whom you’re buying from. You must also inspect the part yourself first, and keep in mind that internal damage is difficult to detect.
How to make sure you’re getting a good quality carburetor
Choose a carburetor with good throttle response. Throttle response is measured by how quickly the engine responds to acceleration requests. When you push your right foot to the floor, you should get a quick response by the engine with minimal lag time. When flooring the gas pedal, it should take less than a second for the tachometer to hit redline. As a standard measure, a carburetor with a CFM (cubic feet per minute) between 500 and 750 should perform well for all of your typical driving situations. Having good throttle response improves your car's performance and maximizes your engine’s potential.
Check the warranty. Particularly if buying a rebuilt carburetor, you want to make sure that the part is guaranteed should something go wrong. Whether buying a new or rebuilt carburetor, you should make sure that your warranty has you covered for up to 100,000 miles.
Buy a carburetor that is easy to tune. This means that all adjustment features, including screws and air filters, are easily accessible in the case that you'd like to adjust the idle air/fuel mixture to your preference.
Keep in mind that carburetors may pose an issue with passing emissions tests required by some states. You want to check your local laws to make sure that the part you’re installing is legal and that your car will still be able to pass the necessary smog testing.
YourMechanic supplies top-quality carburetors to our certified mobile technicians. We can also install a carburetor that you've purchased. Click here to get a quote for a carburetor replacement.
This article originally appeared on YourMechanic.com as How to Buy a Good Quality Carburetor and was authored by Valerie Johnston.