9A-8 F _ Fuel Delivery Systems Fuel Pressure Regulator The Fuel Pressure Regulator (Figure 3) is attached to the fuel supply manifold assembly downs . injectors. It regulates the fuel pressure supplied to the injectors. The regulator is a diaphragm-o ' valve. One side of the diaphragm senses fuel pressure and the other side is connected to the l vacuum. Nominal fuel pressure is established by a spring preload applied to the diaphragm. Bel the diaphragm with manifold vacuum maintains a constant fuel pressure drop across the injectors: of that used by the engine is bypassed through the regulator and returns to the fuel tank. VALVE ENGINE VACUUM ASSEMBLY BALL REFERENCE TUBE SPRlNG SEAT SEAT SPRING I UFFEn FUEL : HOUSING FILTER E g I : SCREEN i DMPHRAGM MOUNTING PLATE N u LOWER HOUSING O-R'NG T FUEL OUTET GROOVE " ' TUBE (RETURN) FUEL INLET TUBE (SUPPLY) M277 Figure 3: Fuel Pressure Regulator Test Point A pressure test point with a Schrader fitting is in the engine fuel rail to relieve pressure in the fuel measure the injector supply pressure for service and diagnostic work. Refer to Caution and Warn 1994 Pawertrain Control/ Emissionsn