Ford Repair: Fuel evaporatorsystem, ford mustang cobra, negative battery cable

Question
     Hello! I´m a Swedish guy who drive a 1996 ford mustang cobra 4,6l. My "checkengine" light turns on after driving the car for about 30-45min,
I have tried a several times to take of the negative battery cable trying to zero the system, it works but the checkengine light always come back.
  For about a month ago I bought a Superchip troublecode reader when using the tool it indicates trouble with the fuel evaporatorsystem.
  Have you got any tips? What may cause the problem? as far as I can understand the problem is located before the canister. I would be very greateful for any help! By the way I´m not sure about the service history.
                       Regards / Johan  

Answer
Hello and thanks for the question...I'll try to help.
I would look at the gas cap as a possible failure point. What it is telling you is that the EVAP system has failed. What you need to do is figure out IF it is an electrical problem or a sealing problem. Also, check the EVAP electric motor for an open.
Hope this helps,
Erik