I have a 98 1500 GMC, I have had a tune up and replaced the fuel pump and numerous other parts within the last 6 months. Once its started on most mornings she drives like she did when she came off the lot. However lately i have to pump the gas pedal several tiems while turning her over to get it to start. Also if i take off the manifold and pour gas directly into the throttle body it will turn over like a charm. Like I said, i dont know what is left to replace, it will run a little rough going to work uphill once i leave my house like its nto getting enough gas. However after that it runs like a charm up those same hills later in the day. Any ideas?

 

is it a 5.3? There uis a fuel regulator that is probably the culprit.

 

Fuel Pressure Regulator | 1996 Chevrolet C1500 1/2ton P/U 2WD 8 Cylinders M 5. This is for a 96, however they are all the same at least through 2000.
Pull the hose off it, if you get fuel there, it is bad.

 

That was the last thing replaced on it in feb 2012. i will check it out right now to make sure they actually replaced it.

 

I checked the purge valve and it was full of fuel. No check engine light or anything like that. Truck is running fine now but this morning it needed the gas pedal to be pumped.