Like any other mechanical equipment, the fuel pressure regulator can also fail, leading to many problems. The most important of those, is excess fuel entering the engine.Does your car emit a thick, dark smoke, or some oil, from the tailpipe? Has its mileage dropped? A bad fuel pressure regulator can be the reason of these problems. The fuel injection system in the car must supply fuel to the car engine with a constant optimal pressure. A spring inside the pressure regulator pushes against the diaphragm and helps regulate the pressure inside it. The tension (pressure) in the spring is preset by the manufacturer to get the desired fuel pressure. The fuel pump has to push enough fuel at the critical pressure to overcome the spring tension. The additional fuel that is not needed is sent back to the fuel tank through the fuel return line.
Location and Working of the Fuel Pressure Indicator
To find out where the fuel pressure indicator is, you need to follow the fuel rail around the car engine. The fuel rail is a pipe that carries fuel to the injectors and to the cold start valve in the engine. The cylindrical metallic object connected to the fuel rail is the fuel pressure regulator, which is the last component of the engine that is supplied with fuel. It has a vacuum hose attached to it. The vacuum in the regulator provides the extra pressure against the spring. Due to this vacuum hose, when the vehicle is at an idle condition, there is less pressure against the fuel coming inside the regulator. When the vehicle accelerates, the fuel entering the regulator increases. This is how the fuel requirement in the engine is served accordingly.
Bad Fuel Pressure Regulator Indications
Fuel pressure regulators do not fail all that often. However, if they do fail, then it may result in low fuel pressure. Mostly, the diaphragm develops a leakage and the fuel enters the vacuum hose. This may lead to various kinds of problems in the engine. The pressure in the regulator can be checked by pinching the fuel return line. If the pressure in it does not rise after pinching the fuel return pipe, it means there is loss of pressure. A sufficient fuel pressure is not built inside the regulator. You will also notice black smoke and oil coming from the exhaust (implying rich engine running). Even when the engine of the car is turned off, the fuel pressure drops.
Signs of a Bad Fuel Pressure Regulator