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  5. BBD Accelerator Pump Circuit
BBD Accelerator PumpWhen the throttle is pressed, the engine will get the extra fuel it needs via the accelerator pump circuit. This gets the engine over the hump until the main, or power circuit takes over.

Fuel enters the accelerator pump well through the inlet check valve. The slight pressure, or weight of the fuel lifts up the check ball and allows fuel to flow into the well. This is done as the pump raises up.

As the throttle lever is moved, the accelerator pump is forced down sending fuel to the main discharge and into the carburetor bore. Pressure from the pump piston holds down the inlet check ball so that fuel doesn't bleed back to the float bowl.

Trouble Shooting Your Accelerator Pump

The lag can be caused by the distributor advance not working correctly.

A lean condition could cause a lag including popping through the carburetor.

A rich condition could cause a lag.

With those conditions out of the way lets see about the accelerator pump circuit.

Has the vehicle been sitting for a long time? This might cause the check balls, inlet and outlet to get varnished up causing them to stick. The passage itself could be varnished and plugged.









Adjusting Accelerator Pump Stroke
1955 Chrysler
BBD Pump Circuit

  • Back the idle screw out so it is not touching the fast idle cam.
  • Open the choke valve to get the throttle valve to close.
  • Install the throttle connector rod in the outer hole of the throttle lever and the inner hole of the pump arm.
  • The B distance is 1" from the top of the float bowl cover to the top of the plunger shaft.
  • Adjust by bending the connector rod as illustrated.
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