During several ground schools lately we've gotten the feeling that some misunderstanding exists about how a carburetor's accelerator pump works on an aircraft engine. And, here we’re talking about carburetors on 1820’s and larger, the float carburetors on 985’s and 1340’s are a different story. Some believe that a rapid throttle movement (with the engine at rest before start) causes a "squirt" of fuel into the throat of the intake, in much the same fashion as your 76 Belchfire V-8 automobile parked out in the garage.
Actually, you just might be tempted to ask, “Why do we need or have an accelerator pump in the first place”? Well, without one, every time you advanced the throttle, you’d likely be confronted with a “stumble” or hesitation, as well as experiencing a backfire almost every time.
Let’s take a look at just how the pressure injection xx carburetors accomplish this task.
R. L. Sohn 1997 ©
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