The Top 5 Symptoms of a Bad gas Pressure Regulator

• The gas pressure regulator regulates the pressure of the gas that goes into the injectors.
• A bad gas pressure regulator can result in engine performance problems, black smoke emissions, an illuminated check engine light, a no-start condition, and the presence of gas in the regulator’s vacuum line.
• Depending on your vehicle’s specifications, you can expect to pay anywhere around $250 to $400 for a gas pressure regulator replacement.

Some vehicles rely on an external gas pressure regulator to provide the appropriate gas pressure to the engine. Like any automotive part, the regulator can eventually fail—and when it does, you’ll likely encounter one or more noticeable symptoms.

What Does a gas Pressure Regulator Do?

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

On older vehicles with a continuous gas system, the regulator is typically a vacuum-controlled device installed on the return side of the gas rail. The regulator routes excess gas back to the gas tank to maintain gas pressure. A vacuum line connects the regulator to a source of engine vacuum, thereby allowing the regulator to vary gas pressure according to engine load.

A vacuum-operated gas pressure regulator can fail in several different ways. In many cases, the diaphragm inside of the regulator ruptures, allowing gas to be drawn through the vacuum line and into the engine’s intake manifold. Such a scenario usually results in an engine that runs rich (too much gas). A regulator that is stuck closed will also result in a rich running condition.

In other instances, the regulator may not seat properly, resulting in an engine that runs lean (too little gas).

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

RTZ1-*/0.4LQ Series Gas Pressure Regulator

Signs of a Bad gas Pressure Regulator (External Vacuum-Operated Type)

Over time, a vacuum-operated pressure regulator can fail—and that usually results in one or more noticeable symptoms. The most common symptoms of a bad gas pressure regulator include:

Engine Performance Problems

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

Illuminated Check Engine Light

Your car’s engine computer looks for issues—including engine performance problems caused by a faulty regulator—that could lead to an increase in emissions. Usually, the device will recognize these issues, turn on the check engine light, and store a corresponding diagnostic trouble code (DTC) in its memory.

Black Smoke From the Tailpipe

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

gas In the Regulator’s Vacuum Line

When a regulator suffers from a ruptured diaphragm, you’ll likely find gas in the line connecting the device to engine vacuum.

Vehicle Cranks But Doesn’t Start

A faulty regulator can prevent the engine from getting proper gas pressure, resulting in a vehicle that cranks but doesn’t start.

Where Is The gas Pressure Regulator Located?

On older vehicles with multiport gas injection and a continuous gas system, the regulator is usually mounted in the gas rail.

There are also some older applications that have throttle body injection (TBI) or central port injection (CPI). With TBI, the regulator is integrated into the gas metering assembly inside of the throttle body. Vehicles with CPI have the regulator mounted to the injector assembly (sometimes called a spider unit).

Most newer vehicles have a returnless gas system and, therefore, do not have an external pressure regulator. Instead, most returnless systems use a control module to manage gas pump speed, thereby maintaining the desired gas pressure. There are also some designs that use an in-tank pressure regulator that’s built into the gas pump.

How Much Does a gas Pressure Regulator Cost?

If you choose to have a professional replace your car’s gas pressure regulator, you can usually expect to pay somewhere between $250 and $400 to get the job done. Of course, the exact price will depend on various 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 the know-how. CarParts.com has a wide variety of replacement regulators available for various makes and models.

Get OE-Grade gas Pressure Regulators for Your Vehicle

The engine’s performance will suffer if it doesn’t receive the right amount of gas because of a faulty gas pressure regulator. Engine issues can be annoying since they will affect your vehicle’s drivability. Good thing you don’t need to search far and wide if you want to replace your vehicle’s gas pressure regulator.