THE Huangpu District Court of Shanghai yesterday turned down an appeal by dissident Fu Shenqi against his three-year sentence to a re-education-through-labour camp in Jiangsu. Fu, whose activism dates from the late 1970s, was detained in the summer for allegedly instigating a hunger strike by four other Shanghai dissidents. It was the second time that Fu's appeal, lodged in the form of a civil litigation against the Government, had been turned down. His relatives in Shanghai claimed yesterday the Huangpu court had violated its own regulations by not allowing Fu to appeal in court and by not conduct-ing an open hearing. ''We were told the hearing would start at 1 pm'', a relative said. ''Yet when we went there at 12.45, we were told the verdict had already been made. We were not shown any documents''. Relatives said Fu's wife, Li Liping, who engaged in a long dispute with court officials, had been detained.