I am sorry I cannot be of much more help than to say that the English is not of a high standard and does not really make much sense. I can say however that 'sure fire' means definite or certain.
I believe that 'pass the smell test' would derive from something like someone checking if food is off or not by using their sense of smell to check it. A much stronger derivative would be from a much ruder phrase in English "bullshit". You may hear people say 'there is a funny smell in here' when someone has said something they do not believe to be true, in the sense that their comment is or smells of 'bullshit'. Although rude and swearing, this word is very commonly used in the UK (however not normally in professional situations).
The meaning of the phrase is that if something passes the smell test then it holds weight, is legitimate and reliable (at first glance).
Hope this is of some help but I really do not know what an equivalent in Spanish would be.
The translation workplace 
