Hi i just have a quick question about using jumper cables. All of the instructions I have ever read say to attach the negative cable of the dead battery to the engine block of the vehicle and not to the battery post. I have jumped several vehicles as well as mine multiple times and following this instructions it has never worked. The only way I can get it to work is to attach the negative cable not to the engine block but to the post. Why do is it the way I am told to do it, doesn't work but the other way does? Thanks