Engine vacuum, atmospheric pressure and spring tension all work on the vacuum modulator diaphragm. Which of the following statements describes the action of these forces on the diaphragm?
A) As manifold vacuum increases, it works with atmospheric pressure to stretch the spring, increasing modulator pressure.
B) As manifold vacuum decreases, the spring extends, increasing modulator pressure.
C) As atmospheric pressure changes, there is an inversely proportional change in modulator pressure.
D) As manifold pressure changes there is a directly proportional change in modulator.

Question

Quizplus · Accepted Answer

As manifold vacuum decreases, the spring extends, increasing modulator pressure, because the spring is pushing against the diaphragm with less vacuum to counteract it.

Engine Vacuum, Atmospheric Pressure and Spring Tension All Work on the Vacuum