I am puzzled, I'd appreciate some advice. Here's the timeline of events... last fall I was losing fuel pressure after it rose upon turning the key. It would drop almost immediately after rising to 30-40. I went through a series of checks, and determined the fuel sending unit to be bad, as when I crimped the return hose, the pressure held. I replaced the sending unit and never had a problem again. This winter I installed new Bosch III injectors from FIC. While I was there, I also replaced the pressure regulator with a new AC Delco one, because it was original and I had easy access to it. I drove the car several times with no problems at all, until recently when I have difficulty starting it. I checked the pressure and same scenario... loss of pressure after initial turn of key. I checked the sending unit by crimping the lines... unlike last time, the pressure drops when I crimp the return lines. I see no gas leaks at the pressure regulator nor the injectors. I can't imagine a new regulator or my $500 injectors are leaking... but any advice would be appreciated. The car drives fine, but since I loose initial pressure, it takes forever to start.

It's a base model 1990 convertible.

 

If you pinch off return line, and pressure drops that fast, I would think your new fpr is not good. I don’t think injectors would leak that fast

 

When my adjustable fpr went last year, it reeked of gas in the area of the fpr. The hoses reeked too. The diaphragm had a crack in it. Lost fuel pressure over a minute or so.

There’s a pulsator in the tank which a lot of people replace with a piece of fuel hose. I think this can cause your symptom too.

I doubt injectors leaking past internally. They can leak by orings or at the fuel rail to line connections.

 

I also thought FPR with it going down that fast. I honestly just put in a brand new AC Delco one 3 months ago. I just couldn't imagine it's bad.