need carb help
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Joined: Aug 2000
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From: (near) Denver USA
If you're referring to the fuel pump, its function is to provide fuel to the carb fuel bowl, on demand, as determined by the float level. When the bowl contains adequate fuel, the float closes the inlet needle valve to prevent flooding (i.e., fuel pump overfilling the bowl).
All of the fuel that the carb uses in any operating mode (idle, main, or enrichment) comes from the bowl, so the bowl must be supplied with fuel to keep from running out. You can disconnect the fuel pump temporarily and allow the engine to run on the fuel in the bowl, but it will not last very long, even at idle. When the fuel in the bowl runs out, the engine will stop running.
At idle, only the carb's idle circuit (regulated by the idle mixture needles) should supply the fuel/air mixture to the engine.
All of the fuel that the carb uses in any operating mode (idle, main, or enrichment) comes from the bowl, so the bowl must be supplied with fuel to keep from running out. You can disconnect the fuel pump temporarily and allow the engine to run on the fuel in the bowl, but it will not last very long, even at idle. When the fuel in the bowl runs out, the engine will stop running.
At idle, only the carb's idle circuit (regulated by the idle mixture needles) should supply the fuel/air mixture to the engine.
Moderator
Joined: Dec 2001
Posts: 22,436
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From: Louisville,Ky.
The pump is the accelerator pump. It is only used when opening the throttle to compensate for the added air being drawn in until the vacuum signal in the venturies draws fuel thru the booster venturies to keep it running.
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monkey jason
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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Apr 8, 2013 05:23 PM
