Which port gives indication of an O-ring failure or a damaged O-ring?

• A. Port A
• B. Port B
• C. Port D
• D. Port C

Answer: (C)

O-ring failure allows a leak path between the two chambers it seals, so you detect it by a port that is wired into the leak-detection or diagnostic path of the system. This port is specifically there to sense blow-by or pressure changes when the seal isn’t intact. The other ports are used for normal operation—supply, exhaust, or isolation—and won’t reliably indicate a seal leak because they aren’t connected to the leak path. So the port tied to the leak-detection circuit will show a signal (pressure/flow) indicating the O-ring is damaged.