Hi.. i was a certified tech for 20+ years.not having wrenched on newer cars(97 and up) my expertise is lacking,,so if somone could help me out i'd greatly appriciate it..Back in july my 99 GMC Jimmy didnt want to start in the mornings,,battery was fine..it just cranked and finally would start rough..did this for a few weeks..finally i gave it a shot of starting fluid and it fired right up and ran fine...i notice if i cycle the key a few times it trys to fire but just coughs..i know it's a fuel problem but i've been told it could be somthing call a TANK PREASURE SENSOR...OR EVEN THE PUMP..it's out of my leauge right now..any advise would be great..i'm unemployed so taking it to a shop is out,,,need to be dependable cuz my wife is disable and i need to get her places,,,thanks alot,,,,Mike,,,248-303-0959,,oh yeah,,fuel preasure is with in limits.....

If the fuel pressure is good and is hard to start and runs rough until it warms up then it could be a intake gasket or temp sensor.

If it is the vortec motor I have seen the individual injectors fail in the past. Also have seen the individual hose under the intake for the injector split also. Do you have a scan tool the shows data stream? Watch the coolant temp sensor to make sure it is reading accuratly. Also like the previous post says upper or lower intake gasket.