check your fuel lines for a restriction.you may have a kink in one of the hoses or steel lines.if that dont work,take the line off the fuel pump and tank and try to blow air through it.if you can blow air through it,you did something wrong when you installed the sending unit.make shur your fuel pump is working before you do anything.pour some gas in the carb and put your finger over the inlet of the fuel pump to see if it is sucking.