Technician A says that vacuum-operated fuel pressure regulators maintain an equal pressure drop across the fuel injectors all the time. Technician B says that intake manifold pressure is high at idle. Which technician is correct?
A) Technician A only
B) Technician B onlyC) Both technicians A and B
D) Neither technician A nor B

C) Both technicians A and B

Explanation:

Fuel pressure regulators are a vacuum operated spring-loaded diaphragm that enables a vehicle's fuel delivery system to maintain a constant pressure. When the vehicle is at idle the regulator is open allowing fuel to bypass the delivery system and go back into the tank.

In pounds per square inch, the atmosphere exerts 14.7 PSI at sea level on average. The vacuum inside an engine's intake manifold, by comparison, can range from zero up to 22 inches Hg or more depending on operating conditions. Vacuum at idle is always high and typically ranges from 16 to 20 inches Hg in most vehicles.