Fuel pressure

[bakogian]

Good morning. I would like to ask you something about a f225 i have. The ful pressure must be 40 psi after shut down the engine or must drop to 0 immediately? I had a starting problem and my mechanic insist that must drop to zero

[boscoe99]

Most EFI systems will maintain fuel pressure for a while after the fuel pump stops running. Loss of fuel pressure very quickly usually denotes a pressure regulator that is going amiss.

Not sure how a regulator that fails to hold pressure when the pump is not running would affect a starting issue. Assuming the fuel pressure is at rated pressure when the key is first turned on or when the motor is being cranked.