Why is fuel rail pressure critical in direct-injection engines, and how would you diagnose rail pressure issues?

• A. Injectors require stable high pressure for proper atomization; rail pressure issues cause misfires, rough idle, or no-start; diagnose with a rail pressure gauge, and inspect pump, regulator, and system leaks.
• B. Rail pressure has no impact on engine performance.
• C. Rail pressure only affects cold starts.
• D. Direct injection engines operate at low rail pressure.

Answer: (A)