If there was sugar put into your gas tank, changing your fuel filter and having the fuel injection system cleaned would be the first logical course of action. If you changed the fuel pump before you changed the fuel filter you may have damaged the new fuel pump. More info would help.
If the sugar is not much then just change the filter and if its a lot then you will have to remove the tank clean it out and then replace the filter and flush out the fuel lines. It is hard but it works.