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Fuel Pressure Regulator - Houston's Premier Auto Repair Facility

Fuel System Home Page > Parts of the Fuel/Engine Management System > Fuel Pressure Regulator


Function: Controls the fuel pressure going to the fuel injectors.


Signs of Wear: Engine knock, lack of power, engine smoke increased exhaust emissions, poor fuel economy.














The fuel pressure regulator controls the pressure inside the fuel injector rail. As pressure inside the rail increases, the diaphragm in the regulator pushes the pintle valve open, allowing more fuel to return to the fuel tank, and decreasing the pressure in the fuel injector rail. As fuel pressure drops close to the minimum specification, the pintle valve closes, increasing the fuel pressure in the injector rail. The pressure regulator continuously works in this way to keep fuel pressure constant. The fuel pressure regulator is usually operated by engine vacuum to slightly increase fuel pressures as engine load is increased. As engine vacuum is increased - normally during engine idle or lower speed cruising, the pintle valve inside the regulator opens, allowing a decrease in pressure in the fuel injector rail. If engine vacuum decreases, the pintle valve closes, increasing fuel pressure inside the rail.


The diaphragm operates the pintle valve inside the regulator, and also serves as a barrier between the fuel system and the air intake. If the diaphragm develops a hole, fuel can leak into the air intake of the engine causing, causing it to run at incorrect air/fuel mixture. The effects of a leaking diaphragm inside a pressure regulator are seen mostly at idle, when engine vacuum is high. It is also noticed when the vehicle is started, after sitting for some time. After the vehicle is turned off, excess fuel pressure leaks through a failed diaphragm into the intake manifold. This extra fuel in the intake manifold causes the enfine to be hard to start, and to run rough for the first few seconds after start-up.


The fuel pressure regulator uses engine vacuum to open and close the pintle valve, allowing fuel to leave the injector rail.


A fuel leak into the intake manifold can cause the engine to run rough due to incorrect air/fuel ratio.


Have your vehicle fuel and engine management system checked by an ASE Certified Technician in Fuel System Services. Schedule service today to visit our repair facility on the southwest side of Houston.