During cranking, which bypass valve blocks fuel flow to the main jet to build pressure?

• A. Idle
• B. Main
• C. Pilot
• D. Auxiliary

Answer: (B)

During cranking, the fuel metering system uses a path that bypasses the main jet so pressure can build in the metering chamber without leaking through the main jet. The valve that does this is the main bypass valve. By blocking flow to the main jet, fuel pressure rises in the starting circuit, helping deliver a rich starting mixture when ignition occurs and then returning to normal metering once the engine starts. The other bypass routes govern only their respective circuits (idle, pilot, auxiliary) and aren’t responsible for building pressure in the main metering path during cranking.