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Common Failures Of The Fuel Pressure Regulator: Defects And Signs!

Some vehicles rely on an external fuel pressure regulator to provide the proper fuel pressure to the engine. In this post we will tell you what are the symptoms and common failures of the fuel pressure regulator , and thus attend to them quickly and avoid major expenses.

Like any automotive part, the regulator can fail over time, and when it does, you’ll likely encounter one or more noticeable symptoms.

What is the function of the fuel pressure regulator?

A fuel pressure regulator does what its name suggests: It regulates the pressure of the fuel going to the fuel injectors.

On older vehicles with a continuous fuel system, the regulator is typically a vacuum controlled device installed on the return side of the fuel rail.

The regulator directs excess fuel back into the gas tank to maintain fuel pressure. A vacuum line connects the regulator to an engine vacuum source, thus allowing the regulator to vary fuel pressure based on engine load.

A vacuum actuated fuel pressure regulator can fail in a number of ways. In many cases, the diaphragm inside the regulator ruptures, allowing fuel to pass through the vacuum line and into the engine’s intake manifold. This situation usually results in an engine running on too much fuel. A regulator that is stuck closed will also result in a rich run condition.

In other cases, the governor may not seat properly, resulting in an engine running low on fuel.

It is important to note that most modern vehicles have a returnless fuel system that does not include an external fuel pressure regulator. Instead, most returnless systems use a control module to manage the speed of the fuel pump, thus maintaining the desired fuel pressure. There are also some designs that use an in-tank pressure regulator that is built into the fuel pump.

Where is the fuel pressure regulator located?

On older vehicles with multi-port fuel injection and a continuous fuel system, the regulator is usually mounted on the fuel rail.

There are also some older applications that have Throttle Body Injection (TBI) or Center Port Injection (CPI). With TBI, the governor is integrated into the fuel metering assembly inside the throttle body. Vehicles with CPI have the regulator mounted on the injector assembly (sometimes called a spider unit).

Most newer vehicles have a returnless fuel system and therefore do not have an external pressure regulator. Instead, most returnless systems use a control module to manage the speed of the fuel pump, thus maintaining the desired fuel pressure.

There are also some designs that use an in-tank pressure regulator that is built into the fuel pump.

Common signs and faults of the fuel pressure regulator

Over time, a vacuum-operated pressure regulator can fail, and that usually results in one or more noticeable symptoms. Common fuel pressure regulator failures include:

1- Engine performance problems

A faulty fuel pressure regulator can cause a loss of fuel pressure. As a result, the engine may exhibit performance problems such as hard starting, rough running, stalling, and lack of power.

2- Illuminated check engine light

Your car’s engine computer looks for faults (including engine performance problems caused by a faulty governor) that could lead to increased emissions. Typically, the device will recognize these problems, turn on the check engine light, and store a corresponding Diagnostic Trouble Code (DTC) in its memory.

3- Black smoke in the exhaust pipe

A faulty fuel pressure regulator can cause the engine to run rich. In extreme cases, this condition can cause the vehicle to emit black smoke from the tailpipe.

4- Fuel in the vacuum line of the regulator

When a regulator suffers from a ruptured diaphragm, you’ll likely find fuel in the line that connects the device to the engine’s vacuum.

5- The vehicle starts but has no power

A common fuel pressure regulator failure, is a faulty regulator that can prevent the engine from getting proper fuel pressure, causing the vehicle to start but lack power.

How much does a fuel pressure regulator cost?

If you decide to have your car’s fuel pressure regulator replaced by a professional, you can generally expect to pay between $250 and $400 to do the job. Of course, the exact price will depend on several factors, such as the year, make and model of your vehicle. You can save money by replacing the regulator yourself if you have the tools and knowledge.


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