What effect does low manifold vacuum have on fuel pressure regulation?

Low manifold vacuum typically increases fuel pressure in a fuel injection system. This occurs because fuel pressure regulators often operate based on the vacuum level in the intake manifold.

When manifold vacuum is low, indicating that the engine is under a heavier load or at wide-open throttle, the fuel pressure regulator responds by allowing more fuel pressure to be delivered to the fuel injectors. This is necessary to ensure that a proper fuel-to-air ratio is maintained, as the engine is drawing in a larger volume of air and requires more fuel to match that air intake for optimal combustion.

In this scenario, the regulator compensates for the lower vacuum by providing higher fuel pressure, which is crucial for maintaining performance and efficiency. This regulation is important for fuel atomization and ensures the engine runs smoothly even under varying conditions.