What position of a pressure injection carburetor manual mixture control would stop engine operation?

• A. Idle cutoff
• B. Full rich
• C. Auto lean
• D. Mid-range

Answer: (A)

In this context, the manual mixture control position that stops engine operation is idle cutoff. When set to idle cutoff, the fuel flow to the engine is shut off, so no fuel reaches the cylinders. Without fuel for combustion, the engine can’t run even though ignition is present, and it dies. The other positions adjust how much fuel is allowed to flow for different operating ranges (full rich provides more fuel for starting and low-speed operation, auto lean reduces fuel for cruise, and mid-range balances fuel for mid-throttle). None of those fully cut off fuel, so the engine continues to run.