Carburetor Accelerator Pump
What Is a Carburetor Accelerator Pump?
The accelerator pump is a small, precisely engineered component found within a carburetor, typically driven by a solid piston or a flexible diaphragm that is mechanically linked directly to the throttle mechanism. Its fundamental purpose is to temporarily and rapidly enrich the air-fuel mixture the moment a driver quickly opens the throttle — without this immediate delivery of extra fuel, the engine would experience a noticeable stumble or hesitation during rapid acceleration, compromising drivability and performance.
How Does the Accelerator Pump Work?
When the throttle is snapped open, air rushes into the carburetor much faster than fuel can follow through the main metering circuit. An accelerating pump is used to provide the correct air-fuel mixture during this transition — the pump receives fuel from the float chamber and discharges it directly into the mixing chamber when the throttle valve opens. Once sufficient pressure builds, a measured, high-velocity shot of atomized gasoline is ejected through the discharge nozzle — called the squirter — which is strategically aimed directly into the primary bore of the carburetor throat, ensuring immediate mixing with the incoming air charge. Once the throttle movement stops, a return spring pushes the piston or diaphragm back to its original position, creating a vacuum that refills the chamber and prepares the pump for the next rapid acceleration event.
Why Accelerator Pump Condition Matters
Many symptoms can indicate a failing accelerator pump. One common sign is sluggish acceleration, which happens because the engine doesn't receive enough fuel. The issue can become severe enough to cause sputtering or even stalling, and other signs include hard starting or hesitation during acceleration. For carburetor-equipped classics, muscle cars, and hot rods, the accelerator pump is often the first component to degrade over time due to its rubber diaphragm or cup material breaking down from heat and fuel exposure. Replacing or upgrading this small part can dramatically restore throttle response.
Tuning and Upgrading Your Accelerator Pump
Some carburetors allow detailed tuning based on vehicle specs — you can adjust for weight, gear ratio, and specific performance needs. Modified or high-performance engines often need more fuel on demand, requiring larger pump nozzles and stronger diaphragms. One key tuning principle is that the ideal accelerator pump tune is the least amount of fuel required to create optimal acceleration — more is not always better, as excess pump fuel can actually cause bog under heavy throttle.
Top Brands for Carburetor Accelerator Pumps
Quick Fuel Technology is one of the most respected names in performance carburetion. Founded in 1998, Quick Fuel Technology has grown into the benchmark by which performance carburetors are measured. Their accelerator pump lineup includes complete kits with aluminum housings, diaphragms, pump arms, cams, and hardware — featuring an exclusive streamlined nozzle design that reduces pull-over at high RPM, with each squirter stamped for identification and sold with replacement gaskets.
Edelbrock brings decades of manufacturing expertise to their accelerator pump offerings. Founded in 1938 and recognized as one of the nation's premier designers and manufacturers of performance replacement parts, Edelbrock produces their core products in the United States using state-of-the-art equipment. Their accelerator pump assemblies feature Viton cups and are precision-matched to their Performer Series and Thunder AVS carburetor lines, with dedicated pump cam kits that allow fine-tuning of stroke capacity and the timing of the fuel shot through different cam lift profiles and ramp shapes.