Fuel pressure regulator: operation, usefulness and failure

The usefulness of fuel pressure regulator it is basically to control and keep the fuel pressure constant. In this way it avoids damage to other components such as the injectors or the fuel system ducts. In addition, it contributes to the optimal functioning of the engine and to a better use of combustion.

This regulator also allows fuel return towards the fuel tank, in case the pressure is too high. So it also has the ability to generate a flow back.

How does the pressure regulator work?

To fulfill that function, the regulator is connected to the fuel lines. If the pressure in them is excessive, let the gasoline out through a valve that opens the return line to the tank. Its operation depends on whether it is mechanical or electrical:

mechanical pressure regulator

It consists of a metal container, pressure springa membrane and a Válvula. Its mechanism is very simple because it consists of two parts separated by said membrane. As you can see in the image, one with a black background, in which the fuel is, and another with a white background, in which there is a spring that presses the membrane downwards.

El spring (or dock) is calibrated to tighten the membrane with a specific pressure. If on the other side of the membrane, the fuel has more pressure than the spring has, will push the membrane up. At which point the valve will open and free the passage through the return line to the fuel tank. In this way the pressure drops and the spring will close the passage of fuel through the return.

Now, the fuel pressure needed by the engine is not always the same. For this reason, there is a system that makes it possible to compensate for the pressure exerted by the spring on the membrane: a vacuum system. Effectively, the spring side is connected directly to the intake manifold or manifold (in the image, top right). A place where a certain vacuum is generated, which will “suck” the membrane upwards, compensating for the pressure exerted by the spring. Thus, the fuel pressure necessary to open the passage of the return pipe will be lower.

Examples:

1. The vacuum that is generated in the manifold, and therefore the pressure regulator, is older when the engine is running at idle. A time when the engine needs less fuel. This vacuum compensates for the spring pressure in such a way that the pressure needed to push the membrane is lower. A concrete example is that the fuel pressure required to lift it will be about 10 PSI (0,68 bar) lower.
2. The vacuum which is generated in the manifold is minor or non-existent under full throttle. So the spring force will push the membrane without a compensating vacuum. In this way, the fuel pressure can be higher without lifting the membrane and therefore the return line valve.

Electronic pressure regulator

In this case the pressure regulator has no mechanical components. It works through a solenoid valve, which works with a control solenoid instead of a dock. The pressure is set by a sensorinstead of a direct connection to the intake manifold. In this way, the fuel pressure can be regulated more precisely and efficiently. It is more common to find this type of valve in diesel engines with Common Rail.

Depending on the manufacturer, we can find the pressure regulators in various locations. Although the most common is that it is installed in the distributor duct, or next to the fuel pump.

Related article:

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Why is a pressure regulator needed?

Pressure regulators were designed for electronic fuel injection systems. The engines that worked carburetorThey didn't have this kind of pressure control. It was in the nineties when they began to be incorporated into the engines.

Its need is due to the fact that most of the engine types do not work constantly. Both its speed and its load level vary constantly while we drive our vehicle. This affects the flow of fuel within the car's fuel system, so a system that maintains constant pressure is necessary to protect the injectors.

If this pressure were not at a suitable level, several problems would be caused. For example, if the pressure is very baja, injectors would not atomize the fuel correctly and the detonations would be worse in the combustion chambers. On the other hand, if the pressure were too high, there are many components that could deteriorate, because their tolerance levels would be exceeded.

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Regulator failure and prices

One of the most common problems with pressure regulators is that the fuel pressure valve stays open. The symptom that is noticed is the lack of fuel pressure with which the engine can be turned off. To diagnose this problem, the easiest thing to do is to block the return line that returns the fuel to the tank.

The best thing to do in these circumstances is change pressure regulatorBecause it is not an expensive element if it is mechanical. It usually costs between 20 and 40 euros in any online engine spare parts store. Unfortunately, the electronic pressure regulators can be more expensive. There are for just 30 euros, but there are also models that use regulators of up to 400 euros or more. You can see several examples on Amazon, where you can enter the model for which you are looking for the fuel pressure regulator.

The best thing you can do is buy an original, although there are prestigious brands that manufacture them for each model, as is the case with Bosch. Incidentally, it is one of the electronic component houses that manufacture regulators for car brands.

You must bear in mind that there are models in which fuel filter incorporates pressure regulator. In which case the price does not usually vary much, since the most normal thing is that it costs more or less the same as a separate regulator.

Picture 6 – Bill Abbott