2003 vw gti with vr6 engine, shut off engine for 30 min or more, starts easily, but shut off engine for 5 to 10 min. and it runs for 10 sec. then stalls. restarts easily. happens mostly on hot days, 100 degrees or more. any advice appreciated.
That’s a symptom of vapor lock.
Have the residual fuel pressure tested.
http://eva2.homeip.net/eva2/FU01/ch5.5.3.html
Tester
That test should also show if you have a leaking injector, there shouldn’t be any gas around to allow dieseling.
The link provided is for a CIS gas system so it does not apply. It does sound like the fuel pressure is bleeding off; possibly an injector or leaking fuel pressure regulator.
Another idea, a problem w/the evap system purge valve. It is supposed to be closed during start-up. If it was open it could allow gas from the canister into the engine w/the associated overly-rich symptoms. Usually there would be an evap diagnostic code in computer memory if this was the problem.