The timing of fuel delivery can be altered in high-pressure fuel lines by

• A. Temperature change in lines
• B. Sensor misreadings
• C. Varying engine speed
• D. Bending

Answer: (D)

In a high‑pressure fuel system, the moment fuel is delivered to the injector depends on how quickly the pressure surge reaches the injector. The fuel in the line acts like a waveguide, and the time it takes for that pressure wave to travel to the injector is influenced by the line’s path and geometry. When a line is bent, its effective length and how it interacts with the pressure wave change, which can shift the arrival time of the pressure rise and thus alter the timing of fuel delivery. While temperature changes, sensor readings, or engine speed can influence overall fuel behavior in other ways, they don’t directly modify the pressure-wave travel time caused by the line’s bends.