Mr. Ignorance here again, I've installed quite a few pumps, both submersible and jet-type. I would lay dollars to donuts that it is straight 240V. I've never seen the extra yellow cap wire that you describe, and I'm not familiar with Franklin...
In all of my Pump installs, a 12-2-G fed from a load center goes to a Jct. box converts to THWN in EMT or NM flex, feeds the line side of the pressure switch, and gets converted to the yellow jacketed "pump wire" with red-black-green stripes. From there, the well digger's are responsible.
I have had to troubleshoot the problem where red-black-blue cable was used and the plumbers put black on ground on the pump side, and blue to ground on the panel side... in a $6 Million house!
The pump would run for a few seconds and "short cycle"... It was probably a good thing that the well casing was not bonded to the black wire...
I couldn't figure it out without pulling the pump, though. So you may have to resort to the worst-case-scenario...
If the well has any depth at all, it is almost 99% likely to be 240V... I'm not even aware of a 120V submersible, (probably my lack of info) and I just recently bought a 120V jet-type 1/2 HP for my house which helped to free a circuit up, (and it was only $120!) which was the first of those I've seen around here. (New at Lowes)
My well is shallow, and there is less than 100 feet from my foot valve to the toilet at the end of the line!, so size and HP aren't a concern.
At any rate Steve, I am as unfamiliar with pumps requiring four-wire as you are with them only on a three...
Guess it's the locale?
