The accelerator pump in the Carter BBD carburetor is an essential component for achieving smooth acceleration and preventing hesitation. When the throttle is rapidly opened, the accelerator pump circuit delivers an additional shot of fuel to the engine. This extra fuel helps to compensate for the sudden increase in airflow, ensuring that the engine receives the necessary fuel mixture for optimal performance. Without the accelerator pump, the engine may experience a momentary lean condition, resulting in hesitation or stumbling during acceleration. The accelerator pump circuit in the Carter BBD carburetor plays a crucial role in maintaining a consistent and responsive throttle response.
Back out throttle adjustment screw and open choke valve so that throttle valves seat in bores of carburetor.
Install throttle connector rod in the hole in the throttle lever specified on carb spec page.
The distance (B) from the top of the bowl cover to the top of the plunger shaft should be as specified on the spec sheet.
Adjust by bending pump connector rod.
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.
Fill the float bowl with mineral spirits.
With the accelerator pump inserted in the down position, pull it up to see if the well is filling up.
Push the pump down to see if fluid comes out of the main discharge (venturi removed).
Holding the discharge check ball down pump the accelerator pump. You should feel some resistance from the check ball and little if any fluid leaking past the check ball.
Replace the venturi and pump the accelerator pump to make sure the venturi isn't plugged.