What is the Accelerator Pump all about?

You may not be familiar with the term “accelerator pump”. They’re not part of modern vehicles, but they were widely used on older cars. An accelerator pump is part of a car’s carburetor system and is responsible for spraying fuel into the carb. Essentially, it did part of the job of today’s fuel injectors. While accelerator pumps might not be part of modern vehicles, there are plenty of carbureted cars still on the road, from classics to hand-me-downs, and they all require an operational pump.

In a carbureted car, the accelerator pump is responsible for increasing and decreasing the amount of fuel supplied to the carburetor. It works in tandem with the vehicle’s vacuum distributor, which provides a timing advance to handle acceleration.

The accelerator pump ramps up fuel delivery as the throttle is depressed, providing smooth acceleration. Over time and through use, the accelerator pump will wear, eventually requiring replacement which is usually done alongside a carburetor rebuild. Premature failure is also possible, although not extremely common.

Keep in mind:

• The accelerator pump is part of the fuel delivery system and should never be inspected or replaced except by a trained mechanic.
• The accelerator pump is not inspected during normal maintenance.

How it's done:

• The accelerator pump is verified to see if it needs to be replaced
• The defective accelerator pump is removed
• The new accelerator pump is installed
• The accelerator pump is tested for operation
• The vehicle is tested to ensure proper operation of the accelerator pump

Our recommendation:

Without a working accelerator pump, your vehicle will not respond with smooth acceleration when pressing the gas pedal hard. Slow acceleration will not be affected; this part is only required for fast acceleration. If you suspect your accelerator pump is not working correctly, have one of our expert mechanics diagnose the condition.

What common symptoms indicate you may need to replace the Accelerator Pump?

• Engine does not accelerate smoothly under moderate to hard driving conditions
• Engine stutters or stalls during hard acceleration
• Smoke from exhaust (rich operation)

How important is this service?

The accelerator pump is required in order to deliver smooth acceleration in a carbureted system. If the pump is not working correctly, it could result in either lean or rich operation, both of which will damage the internal components of your engine. Also, poor fuel delivery results in substandard acceleration which may cause you to be a dangerous obstacle in traffic. Have a faulty accelerator pump replaced as soon as you can.