I have thought about this a bit. If I know the input to the valve, I can use low pressure compressed air and the various valve positions to figure which hose connects to which port on the 4-way valve. In other words, if I set the valve to tank, I connect various hoses to the port that has air flowing out until I have air entering the fresh water tank. Same process for :"city" valve selection I should be able to get air flow out of a faucet. Then the valve to pump hose is the only one remaining (I did not disconnect the 4th hose on the bottom of the valve).
My request is that someone who has access to their MH that has the same style valve (With the 4 switch positions in the same place) to reach under the fill port and follow the hose to the valve. Does the hose attach at the left, center or right port on the 4-way valve?
Marked up image valve attached - trying to convey the same as the words above.