Petrol Injection Line Pressure?

Question

Got a question for college and need some help:

A petrol injection system *should* hold 60% LP for 1 min after switch off. *But* all pressure is lost within seconds after switch off. Name 2 possible causes and rectifications.

I know 1 cause is a faulty non-return valve in the pump, which you'd replace, but not sure about another cause. Any help would be appreciated

Answer 1

A leak could be a cause but there is also a fuel pressure regulator somewhere,usually after the fuel rail on the return line.