The position of the trimmer regulator valve is controlled by modulator pressure. During closed throttle or light operation, modulator pressure is ___________.

• A. High
• B. Non-existent
• C. Relatively low
• D. Varied

Answer: (A)

When the throttle is closed or the engine is under light load, the control system uses the modulator to bias the trimmer regulator valve toward limiting fuel delivery. The modulator pressure is applied to the valve so it stays in the position that prevents over-fueling at idle, keeping the engine stable. As load increases and the throttle opens, the modulator pressure changes to allow more fuel. So the modulator pressure is high in closed-throttle or light operation, making that option the correct one.