1994 Ford Fuel Pressure Regulator Diagram & Test Point - Powertrain/Emissions

This is page 9A-8 from the 1994 Powertrain Control / Emissions Diagnosis manual, in the 'Fuel Delivery Systems' section. It describes the Fuel Pressure Regulator, explaining that it attaches to the fuel supply manifold assembly downstream of the fuel injectors and regulates fuel pressure supplied to the injectors. The regulator is a diaphragm-operated relief valve: one side of the diaphragm senses fuel pressure while the other side is connected to intake manifold vacuum. Nominal fuel pressure is established by a spring preload on the diaphragm, and balancing the diaphragm with manifold vacuum maintains a constant fuel pressure drop across the injectors. Excess fuel is bypassed through the regulator back to the fuel tank. Figure 3 (drawing A12772-A) is a labeled cutaway of the regulator identifying the valve assembly, engine vacuum reference tube, ball seat, spring seat, spring, upper and lower housings, diaphragm, fuel filter screen, mounting plate, O-ring groove, fuel inlet tube (supply), and fuel outlet tube (return). A 'Test Point' section notes that a Schrader fitting in the engine fuel rail is used to relieve fuel system pressure and measure injector supply pressure during service and diagnostics, with a reference to a Caution and Warning. Text bleeding through from the reverse side of the page is faintly visible but not part of this page.