Which valve serves to bypass fuel away from the main jet to help build pressure during crank?

• A. Metering Valve
• B. Barrel Valve
• C. Shut-off Valve
• D. Main Bypass

Answer: (D)

Starting an engine efficiently requires fuel pressure to rise quickly during cranking. A bypass path that diverts fuel away from the main jet allows pressure to build in the supply line without being throttled by the metering path. This function is performed by the main bypass valve. Once the engine is cranking or running, the bypass closes and fuel flows through the main jet for normal operation. The metering valve adjusts how much fuel is delivered based on demand, the barrel valve controls flow relative to throttle, and the shut-off valve simply stops fuel flow. So, the valve designed to bypass fuel away from the main jet to build pressure during crank is the main bypass.