[304065]

Ladies and Gentlemen:

Does anyone know why there are THREE hose connections to the fuel pump? I know what they are, S (supply, from tank) D (druck, or pressure to the filter console) and R (return, which is an OUTLET from the pump to the tee fitting). I have the fuel system diagram from the factory manual, but here's what I don't understand-- what is the purpose of the return outlet on the pump? Does it take excess fuel that cannot be forced down the pressure line and send it up the tee, where it then flows against the pressure in the return line from the console and then back to the tank?

Why did they design the pump this way, why not just a feed line to the fuel filter and a return line to the tank? I think it has something to do with the pump being a "roller" type as opposed to a centrifugal type but I would love any clarification on this.

I'm thinking about converting to -8AN lines from my soon-to-be-installed fuel cell all the way to the MFI pump and have found a Mallory pump that has an AN return fitting but would love to know the theory of operation here before I go second-guessing the factory. My guess is that if the braided cloth hose was good enough for RSR's it should be good enough for my 155HP "E" but I am a safety freak . . .