In the Precision Airmotive fuel injection system, what component responds to the mass of air entering the engine to regulate fuel?

• A. A fuel diaphragm
• B. A throttle plate
• C. A flow divider
• D. An air diaphragm that controls a servo ball valve

Answer: (D)

Fuel metering in this system is driven by the mass of air entering the engine, sensed by the air diaphragm inside the metering servo. As air flows through the intake, a pressure difference across the venturi moves the air diaphragm. That movement drives a linkage to a servo ball valve, which modulates fuel pressure to the flow divider. In short, the air diaphragm responds to air mass and, through the servo ball valve, controls how much fuel is metered. The fuel diaphragm responds to fuel pressure, not air mass; the throttle plate governs air flow but doesn’t directly regulate metered fuel in this system; and the flow divider simply distributes the metered fuel.