In the fuel tank
Clean / replace fuel injectors.
It's at the back in front of the fuel tank. Just unplug the connectors and replace the filter.
The ( 2012 ) Ford Fiesta fuel tank is 47 liters ( 12.4 U.S. gallons )
The 2014 Ford Fiesta runs on regular unleaded.
The 2012 Ford Fiesta runs on regular unleaded.
The 2013 Ford Fiesta runs on regular unleaded.
The 2011 Ford Fiesta runs on regular unleaded.
To replace the fuel filler cap on a Ford Fiesta, first ensure the vehicle is turned off. Locate the old cap by opening the fuel door, then twist it counterclockwise to remove it. Take the new cap and align it with the filler neck, twisting it clockwise until it clicks securely in place. Close the fuel door, and you’re done!
Take it to a repair shop.
In the fuel tank
You don't fix it, you just replace it.