Why does my carburetor hesitation?

Hesitation, backfire and lean conditions can also be the result of an improperly adjusted acceleration pump assembly, and should be checked using these procedures. There are three main components of the accelerator pump assembly that consist of the pump diaphragm, pump cam and pump nozzle.

What causes hesitation on acceleration?

A vehicle that hesitates while accelerating or while driving up a hill may have a weak fuel pump. Fuel injectors may become dirty over time and not be able to provide as much fuel to the cylinder as is needed. Dirty fuel injectors may cause the engine to run lean which will in turn, cause hesitation when accelerating.

How do you fix a rich carburetor?

Regardless of whether or not the engine is running too rich or too lean, bring it down to a very lean mixture by turning both screws a quarter-turn at a time, counter-clockwise, then slowly bringing them back up to an equal and smooth mixture.

Why does my Holley 4 barrel carburetor stumble?

If your car or truck is equipped with a Holley four barrel carburetor and stumbles upon acceleration, more than likely the carburetor needs an adjustment to the accelerator pump assembly. This assembly delivers an initial shot of fuel in the right amount, and duration, to provide crisp throttle response right off idle.

How to adjust the accelerator pump assembly Holley?

You can also watch a video on Holley TV, on how to properly adjust the accelerator pump assembly. Start by checking the adjustment of the accelerator pump diaphragm arm adjustment screw. Use a 0.015 feeler gauge to make sure the adjustment is correct. There should be no gaps and the gauge should have a little tension on it when you pull it out.

How do you change the fuel nozzle on a Holley?

Start by increasing the fuel nozzle size up by three sizes. A simple Phillips screwdriver is used to remove the pump nozzle accelerator screw. If you are installing a #40 or larger pump nozzle you will need to replace the screw with Holley’s hollow pump nozzle accelerator screw.

What to do when your carburetor stumbles?

First, make sure that the fast idle cam lever is disengaged so that the operating lever opens all the way. Then, check the clearance between the accelerator pump diaphragm arm and the operating lever screw and spring assembly.