Pontiac Repair: intermittant no start, fuel pressure regulator, pressure guage

Question
1989 Pontiac grand am,2.3 quad4,automatic If I drive it as normal and then shut it off and restart within 10-15 min no problem. If I let it sit for 3-4 hrs no problem. If it sits 1/2 hr to 2 hrs it will crank strong but won't fire if I give it a shot of starting fluid thru the throttle body it will start and run fine. Fuel pump is only 3yrs old and has correct pressure,also replaced fuel pressure regulator. It is not throwing any codes or has CEL. Totally confused. I'm a all around handy guy just not an auto tech.Thanks in advance.

Answer
Hi James:

well when it will not start your going to have to see what's missing. Fuel,or not enough pressure,No injector pulse or no spark. I would hook up a pressure guage on this and see what happens when you tunr thr key off the pressure should hold steady and no bleed off if it does then either the pressure regulator is leaking the check valve in the pump is leaking or the injectors are leakin. choices 1,2 are more likely then 3. also a Noid light in one of the injectorsconnetor to see if you have injetor pulse and lastly a spark cheker to see if you have spark and see what's missing... My guess is the pressure bleeds off to fast and you get a vapor lock and the srarter fluid is just enough to let it run so the pump can catch up to the lack of pressure.. good luck :)