Could you post the diagram of the final solution you came up with? It seems like no one else is using the RS232/RS485 board and I'm having the same problem you are. When you say you jumper Pins 1 and 6 on the shield RS232 port - how did you dp that with a cable installed? Were you using a pigtail cable - with a connector on the pump end and bare wires on the end plugged into the shield's RS-232 port?
A physical diagram would be so appreciated - I wanted to direct message you but it seems that feature is gone. Hope you see this!
It's just that, chances are slim that you will get a reply here. There are instructions in the introductory threads about some simple actions that you need to do, to obtain full posting privileges. I guess mail privileges are tied to the same criteria. It's not much really, just read a certain number of posts, etc. Easily achievable and much better chance of a reply.
Another possible thing, you could treat it as a new problem and ask for general help. With a fresh, full disclosure, someone here might actually know better than that person.
Are you using the exact same setup? Please draw your connection diagram so we can see what is communicating with what.
Handshaking (the added wiring) is only needed if the device that you're talking to requires handshake or if the PC / Arduino software requires it.
In the solution in the other topic, it sounds like the wires were directly soldered on the bottom of the shield. That is actually a bit strange as the pump does not provide handshake signals. So a guess is that the shield is actually communicating with dedicated software on the PC and not with the pump.