I have a problem, i was wondering if anybody has had one similar. My problem being:

When my 96 3.1 is cold it takes about 6 seconds of cranking before it fires ... then it drives completely fine .... and i can stop and it will fire right back up .... UNLESS i let it sit, any more than about 3 hours (it varies) of sitting and it will be hard to start again ....

so when its warm its fine ..... but when it sits its is hard to start.

i was thinking it has something to do with either oil of fuel pressure, something that bleeds down, and has to be built back up before it will fire, but i'm no mechanic.

If anybody has had a similar experience, please share ... any advice is welcome .... thank you.

Welcome to the forum. Your right about your assumption - it sounds like you have a bad fuel pressure regulator; and it can't hold pressure.