my grandfathers car recently wont start at all I replaced the fuel regulator because it was leaking gas but still wont start. i have managed to get it to start 3 times after cranking a few dozen times anmd would restart if i shuit off and restart but not if i let sit for a while

also it is a 2003 buick century 3.1 L

 

We need to know what, if anything, is happening to the fuel pressure.

If the cyls were flooded with fuel , we need to know this. Pull a few spark plugs and see what they tell you.
Let us know what you find and we can go from there..