Shares of FleetCor Technologies are forming a new base while at the same time threatening a sell signal. What’s an investor to do? For those who bought when FleetCor (FLT) broke out past a 134.12 buy point in July, a gain that stretched as much as 12% has been whittled down to almost nothing. That’s not only disheartening but also would be a sell signal if the stock comes all the way back down to 134.12.