Argh! Pumping the gas on a fuel injected car to get it to start

I have a '93 Del Sol with 96K miles, in the last few days it won’t start unless I put my foot down on the gas and even then it stumbles and coughs until the rpms get high and then it idles fine and is okay. It seems to do this if it’s been parked for 12 hours or more, if I start it after a few hours it’s fine. Any ideas? I’m guessing the fuel system is depressurizing, how would I pin point this?

Hook up a pressure gauge to the Shreader valve on the fuel rail, turn the key on to make the pump prime the system and see if the pressure holds.

You might try turning the key to ON and leaving it there a few seconds before trying to start. See if the fuel pump will build up pressure in the lines. You may have to do this two or three times before cranking.

Flooring the pedal when starting is for clearing a flooded engine. I stops or reduces injector firing. If only starts with the pedal down, your flooded. Sounds like you have a leaking injector that floods your engine.