99 ford ranger fuel leak code?

i have a 99 ford ranger and i took it to advanced auto to get it hooked up to see wat was wrong with it cause the check engine light came on ....it came up as a fuel leak code...she said the most common cause for that code was the fuel cap.so i bought one and put it on and she cleared the code..after 37 miles it came back on and now it almost like spits and sputters wen trying to start any ideas wat this code could have been and im kida on a short bugdet and am afraid to drive it cause it wont stay running and i do smell a faint gas smell (wen sitting at light ect.) any ideas or suggestions would be great ..thank you