he tells me it started right up?

alright took my 76 chevy to the truck doctor because of an idling/screeching problem. what happens is that my truck all of a suddens has tons of speed like there is no miss whatsoever. the next day i try to start it up and i smell gas in the cab and it screeches when i try to start it. eventualy i have to pump the gas about 8 times while turning it over to get it to start but wont stay running when i let off the gas. i take it to the shoip the next day they call me and say it started right up and we let it run for a 1/2 hour it seems fine? it happened before thing but ther has to be something wrong. it is a rebuilt starter. i was told the powervalve might have blown out in my carb. but that would not cause the screeching noise would it? sound like the starter was having trouble ingaging but not always. but was still stalling either way. any suggestions? thanks james