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.

Testing the Accelerator Pump

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.











ACCELERATOR PUMP STROKE
1955 Chrysler
  • 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.

BBD Pump Circuit




























1978 (All Models)
  • Remove cover plate on top of air horn. Back off curb idle speed screw to fully close throttle valve. Fast idle cam must be in open choke position
  • Now turn carb idle screw clockwise until it just touches top. Continue two more turns
  • On Dodge/Plymouth models, be sure accelerator pump "S" link is in OUTER hole of pump arb if arm has 2 holes
  • Measure distance between surface of air horn and top of accelerator pump shaft. If adjustment is needed, loosen pump arm adjusting lock screw and turn sleeve to adjust pump travel. When correct measurement is obtained, tighten lock screw.
  • Install step-up piston cover plate and gasket
NOTE: On Chrysler Corp models, if the accelerator pump adjustment is changed, the bowl vent adjustment must be reset


Can't find what you need? Contact Us
TOP