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Autolite 4100 Accelerator Diaphragm

This video illustrates how the accelerator pump circuit works on 1964 and later 4100 carburetors.
4100 Carburetor Parts

1964 & later

How the accelerator pump circuit works:

4100 Accelerator Pump Circuit

When you let up on the throttle the check valve opens and fluid fills the pump chamber.
Pressing on the accelerator puts pressure on the check valve to close it and forces fuel through the bottom hole into the main discharge passage and out the main discharge.

4100 Accelerator Pump

With the check valve installed.
The new check valve has a long stem which you insert into the hole, then pull it through until the umbrella is all the way seated. Trim the stem off so that it doesn’t intrude on the float.

Check Weight

4100 Check Weight measurements. Length is important because it needs room to move up when the check ball moves up to let fuel in.
You can buy a new weight here.

Updated on 12/16/2020

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