carb adjustment/fuel pump
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carb adjustment/fuel pump
1st question, i have a 2bbl motorcraft carb. What exactly does each of the 2 screws at the base of the carb due and what effect does screwing them in and out do.
2nd, after my truck sits for a while i have to pump the exceletator pedal to start it but, why. is my fuel pump allowing fuel to go back to the tank or what?
2nd, after my truck sits for a while i have to pump the exceletator pedal to start it but, why. is my fuel pump allowing fuel to go back to the tank or what?
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Joined: Aug 2000
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carb adjustment/fuel pump
1st answer: Those screws are the idle mixture needles. Turning them clockwise leans the idle mixture, counter-clockwise enriches the idle mixture. They have no effect except at idle.
2nd answer: Heat absorbed from the engine causes the fuel in the bowl to expand and leak through the carb's main and idle circuits into the manifold. This creates an over-rich condition on start-up. Opening the throttle plates allows more air to come in, leaning the mixture for ignition.
2nd answer: Heat absorbed from the engine causes the fuel in the bowl to expand and leak through the carb's main and idle circuits into the manifold. This creates an over-rich condition on start-up. Opening the throttle plates allows more air to come in, leaning the mixture for ignition.
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