Nestled down in the carburetor’s fuel bowl is a little pump that provides extra sprays of needed fuel in situations like starting the car or passing on the highway. Fuel-injected vehicles do not need this pump; it is only present on some older cars with a carburetor, and is also commonly used as a modifier on performance vehicles.
The gasoline that the accelerator pump provides also creates a bridge that stops lag and misfiring as the fuel-delivery system catches up with the engine’s operation. Adjusting the cam in the linkage system of the carburetor allows a larger amount of fuel to be dispensed. A car may have one or two pumps depending on the kind of system.
This pump may be malfunctioning in your vehicle if the car stalls or struggles when taking off hard from a stop. When an accelerator pump fails, it’s normally due to a damaged rubber diaphragm due to wear and tear, and sometimes linkage misalignment. In some carburetors the entire thing must be disassembled to replace it but in others, the repair will only involve removing a few screws.
How to make sure you’re getting a good quality accelerator pump:
Choose a trusted brand name with a good reputation. The accelerator pump isn’t terribly expensive so the difference between a cheap one and a better one is a matter of dollars. Brands like Edelbrock have been around a long time and have established an excellent reputation, particularly in the performance industry.
Consider replacing the entire carburetor at the same time. If the pump has wear, it’s possible the carburetor could stand to be replaced as well, and this takes the guesswork out of matching the parts up.
Make sure you know the laws for your state regarding emissions and the legality of certain accelerator pumps.
This part doesn’t apply to most modern cars coming off the line today, but if you do have an older or performance vehicle, you may need to deal with accelerator pump failure at some point.
YourMechanic supplies top-quality accelerator pumps to our certified mobile technicians. We can also install an accelerator pump that you've purchased. Click here to get a quote and more information on accelerator pump replacement.
This article originally appeared on YourMechanic.com as How to Buy a Good Quality Accelerator Pump and was authored by Valerie Johnston.