91 Q..hard Start...gradually getting worse

[Locknut]

Cars been running fine, idles good, feels smooth..now it's turning over longer and longer to start. It's got a relatively new fuel pump and filter....I thought the fuel pressure regulator may be bad but everyone says they don't go bad...when the car finally catches it sounds like a slight vacuum sucking sound...like the fuel had bleed out of the rail?

[Q45tech]

One connects a tee after fuel filter and measures fuel pressure, then turn off and watch the pressure for an hour over night to analyse any drop below 34 psi.

There is a oneway valve at the fuel pump to protect against backflow and the fuel pump regulator should click shut at 30-33 psi..............even over night you should have 20-25 psi in the morning.

Leaky injectors are rare but leaky fuel hoses and o rings are not.