My 85 IROC with 305 tpi starts fine when cold but after I drive it then park it for an hour or even 2 hours it starts after long cranking. Could it be the fuel pump regulator?

 

Possibly but I would suspect that the injectors are leaking and flooding the engine when it is warm, the extra fuel helps it start when it us cold. Do not just replace parts trouble shoot the problem. Check the basics first, do you have spark and fuel pressure. If yes proceed to check, for leaking injectors, leaking cold start injector, leaking fuel regulator, and is the temp sensir for the engine reading correctly.

 

Check the injector resistance



Then do an injector balance test


Record what you experience on your phone, upload to youtube, which is free and easy.
Also get an ALDU1 cable from moates.net, hook it to a laptop and configure it to run under TunerPro, drive it and log some data to look at fuel trims and sensor info. Or just get a cheap bluetooth scanner from Ebay that will export to a CSV that you can upload to your computer.

 

Beyond possibly being fuel related, a bad cap/rotor can cause this issue. Had this issue on a TPI car that had only 49k miles on it but many of the original (and now 30 years old) wear items in place. Like the others have said though, start with the basics.

 

stock injectors/multecs are notorious for coil failure, especially when they are warm/hot.
As Pro mentioned check the resistance but do it while they are cold and hot.
Let us know how you make out

 

yes, highly likely leaking fuel injector/s or bad fuel pressure regulator diaphragm leaking fuel into that little vacuum line. Easy to test for that.