I think what he's asking is whether or not he can network them together even though they all have the same IP address. And the answer is yes.
As a network engineer, I can think of a way with a Cisco catalyst switch, OR, a linux box with multiple ethernet ports:
Yes, there are a few possible solutions, but I'm surprised that nobody has mentioned the biggest barrier to implementing any of them:
Trying to connect to 8+ pumps at the same time is going to require running 8+ ethernet cables from a central location to each pump. You're going to have cables all over the place, and unless it is done while the gas station is closed it means people driving over the cables, stepping on them, tripping on them and yanking them out of the socket, etc........
And having 8 pumps off-line at a time will probably lead to less-than-cheery looks from the station owner and his customers.