[Dave at Pelican Parts]

On the -4 pumps, there are labels embossed or engraved on the cover: S, D, R. S for "suction", D for "druck" (pressure), and R for "return". Are there any labels on this one?

The port next to the silver cap has to be the return port. In the -4 system, that goes to a Y fitting; one leg of that goes to the tank and the other goes to the return port on the fuel pressure regulator. There is pretty much never any fuel coming out of the R port on the pump, but it's there just in case.

If the other two ports also follow the -4 pump example, the middle is the pressure outlet (which would go to the carbs or the injection), and the one on the right is the suction inlet, which would come from the fuel filter which would in turn hook up to the tank.

--DD