The fuel pressure regulator is a vacuum operated diaphragm relief
valve with fuel pump pressure on one side and regulator spring
pressure and intake manifold vacuum on the other side. The fuel
pressure regulator maintains a constant pressure differential across
the injectors at all times. The pressure regulator compensates for
engine load by increasing fuel pressure as the engine vacuum drops.


These valves can rupture inside and allow fuel to enter the vacuum
line. This is a common cause for hard starting, rough idle for a few
minutes after starting, or stall after starting.
Fuel Pressure Regulator
WARNING LIGHTS