What is Accelerator Pump System in Carburetor?

The accelerator pump system in the carburetor is responsible for delivering an immediate supply of fuel when the throttle is quickly opened. An accelerator pump is a rubber plunger in a cylindrical bore in the car. The bore is full of gasoline, and when you open the throttle (accelerate), the linkage moves the plunger in the bore, forcing a squirt of fuel into the carburetor’s throat. This can result in hesitation, stumbling, or even an engine stall. The carburetor is the main device in an engine for supplying fuel as well as the increment of the fuel pressure. In this article, I will discuss the accelerator pump system in the carburetor. 

Accelerator pump system in carburetor- 

Accelerator Pump System in Carburetor

 

 

For rapid acceleration, the carburetor must deliver additional fuel. By quickly opening the throttle valve for rapid acceleration, the suction through the carburetor increases suddenly. The air is lighter than the gasoline, rushes into the carburetor very suddenly, and gasoline lags behind the air, thus the mixture becomes lean instead of richer. This condition will exist until the inertia has been overcome, and the gasoline particles have time to respond completely to the increased suction. At this time, additional fuel is most needed to make the mixture rich. An accelerating pump is used to provide the correct air-fuel mixture during acceleration. The pump receives the fuel from the float chamber and discharges it directly into the mixing chamber when the throttle valve is open. 

Operation of an accelerator pump system in carburetor- 

Operation of an accelerating pump system.

 

The figure shows the diagram of the accelerating pump system. The pump cylinder is located in a section of the float chamber and draws fuel from it through the strainer and the intake valve when the pump plunger is raised. The leather-covered piston constitutes the plunger. It is linked to the throttle shaft through the plunger rod, pump-connector link, pump-air assembly, and connector rod. When the throttle valve is opened, the plunger moves downward, thus pushing the extra amount of fuel into the carburetor’s throat. 

 

The length of the plunger stroke can be carried by attaching the connector link to any of the three holes in the pump arm assembly.  A long stroke is used in cold weather, a medium stroke in average weather, and a short stroke in hot weather. The longer the stroke, the richer the mixture will be supplied by the pump to the carburetor. 

 

A small amount of air is trapped between the piston and the top of the fuel level. When the plunger rod is depressed, the trapped air gets compression. It forces the fuel to level the cylinder, closes the inlet valve, opens the discharge valve, and discharges the fuel into the carburetor’s throat through the discharge jet. The tip of the discharge jet is small enough to restrict the flow of the fuel so that the discharge is prolonged till it is forced by the pump travel and the expansion of the trapped air. The prolonging of discharge is fast enough for sufficient time to satisfy the demand of the engine at high speed. 

 

When the plunger is lifted upward back to its original position by the accelerator pedal, it causes a partial vacuum in the cylinder which opens the intake valve, closes the discharge valve, and draws in the fuel from the float chamber. 

 

Advantages of an accelerator pump system in carburetor- 

The accelerator pump system is an important component of a
carburetor. It provides several advantages that improve the performance of
an engine. Below are some of the advantages of the accelerator pump system:

• This system improved throttle response. The accelerator pump system
  provides an immediate supply of fuel to the carburetor when the throttle is
  quickly opened.
• The accelerator pump system in the carburetor reduced engine hesitation. Rapidly opening the throttle can
  cause a momentary lack of fuel flow to the carburetor. It will result in engine
  hesitation. The accelerator pump system compensates
  for this lack of fuel by providing a shot of fuel into the carburetor venturi,
  which reduces engine hesitation.
• The accelerator pump system also helps to
  maintain a smooth and consistent idle by ensuring that the carburetor receives
  a consistent supply of fuel when the throttle is opened and closed.
• The accelerator pump system
  ensures that the engine receives the extra fuel needed for acceleration. It enhanced the overall engine performance. This is especially important in
  high-performance engines where quick throttle response is critical.
• The accelerator pump system helps to
  prevent fuel from being wasted during acceleration. By providing an extra shot
  of fuel only when needed, the system ensures that the engine is not running too
  rich, which can waste fuel.

The accelerator pump system is a simple
and effective solution to the problem of engine hesitation during acceleration.
Unlike other systems that require complex electronic controls or additional
fuel injectors, the accelerator pump system is a mechanical system that is easy
to install and maintain. Overall this is a sustainable product used by the developers. 

Disadvantages of an accelerator pump system in carburetor-

If there are advantages then disadvantages are also there. Some of the disadvantages are mentioned below-

• The accelerator pump system has poor fuel economy. While the accelerator pump system can improve fuel economy during acceleration, it can have the opposite effect at full throttle. This is because the system provides an extra shot of fuel that may not be necessary at high engine speeds, resulting in wasted fuel.
• The accelerator pump system increased emissions, particularly during acceleration. This is because the extra fuel supplied by the system can cause the engine to run richer than necessary, which can result in higher emissions.
• The accelerator pump system is a mechanical system that requires regular maintenance to ensure proper operation. The diaphragm and linkage components can wear over time, which can affect the performance of the system. If the mechanical system faults then significant repair will also hamper.
• This system is incompatible with the electronic fuel system. The accelerator pump system is a mechanical system that is not compatible with electronic fuel injection systems. This can limit the ability to upgrade to newer fuel injection systems that offer better performance and fuel economy.

Conclusion-

Overall the accelerator pump system is an important component of a carburetor that helps to ensure smooth and responsive engine performance during acceleration. Whether you have a high-performance engine or a standard engine, the accelerator pump system can help to ensure that your engine runs smoothly and efficiently.