Pontiac Repair: 1999 Grand Prix 3.8 Fuel System Problem, fuel pressure regulator, vapor locks

Question
My son's 1999 Pontiac Grand Prix has the 3.8 engine NOT supercharged. It starts fine at first, then after you drive it awhile and the engine is warm, it will start if you shut it off and restart within 5 minutes, if you wait about 20-30 minutes like going into a restaurant to eat, you come out and try to start it and it will not start, if it does try to start it smells like lien fuel from the exhaust, it used to do this only in warm weather 90 degrees or more now it's doing it all the time, if you wait about 45 min to 1 hour after the engine is warm it will start fine, he checked fuel pressure and it was about 45 lbs not running but drops down to about 20 lbs when leaving the gauge hooked up and waiting about 20-30 minutes, if the problem is due to low fuel pressure, how does it start after sitting for a longer period of time? any Idea's of what to try or look for?  Thanks.

Answer
Hi Don:

Your on the right track. You either have leaking injectors,Leaking fuel pressure regulator either backto the tank or into the vacuum line or the check valve in the pump is leaking. My gues is it's one of the first 2. what happens is the fuel rail vapor locks if the fule is leaking back into the tank. with less fule pressure the gas in the rail will boil and the engine istryin to run on that hot soak on vaor and that doesn't work so well untill the vapor is expelled into the engine. If the regulator is laking raw gas into the vacuum line the fuel in the rail vaporizes but when you crank it up the raw gas is sucked into the motor and raw gas doesn't burn well. Or lastly the injectors are leaking into the motor and same thing as the regulator leaking into the vacuum line. after the engine is hot shut it off. and pull the vacuum line off the regulator and let it sit and see if raw fuel starts to seep out the vacuum port if so that is the culprit. If not then do this run the engine till it hot. shut it off take the fuel rail up out of the intake leave the fuel lines attached and  put paper towel down and lay the injectors on the paper towel cycle the key to run a few times so the rail is pressurized and let it sit and see if the paper towel get wet after sitting for about 1/2 hour any one that's leaking will show up that way. Good luck :)