Mercury Optimax Models 135, 150, Direct Fuel Injection., Page 166Get this manual
DIRECT FUEL INJECTION
rail until an injector opensA fuel pressure regulator controls pressure in the fuel rails, and allows excess fuel to return into the vapor separatorThe fuel regulator not only regulates fuel pressure but also regulates it at approximately 10 p.s.ihigher than whatever the air rail pressure isThe fuel regulator diaphragm is held closed with spring that requires 10 p.s.ito force the diaphragm off the diaphragm seatThe back side of the diaphragm is exposed to air rail pressureAs the air rail pressure increases, the fuel pressure needed to open the regulator will equally increaseExample: If there is 50 p.s.iof air pressure on the air rail side of the diaphragm, 60 p.s.iof fuel pressure will be required to open the regulatorThe return fuel line to the vapor separator is water cooledTo equalize the pulses developed by the pumps (both air and fuel) tracker diaphragm (3) is installed in the starboard railThe tracker diaphragm is positioned between the fuel and air passagesThe tracker diaphragm is rubber diaphragm which expands and retracts depending upon which side of the diaphragm senses the pressure increase (pulse)