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Flow Control: How Does A Fuel Pressure Regulator Work?

A fuel pressure regulator

How does a fuel pressure regulator work? In brief, it’s an essential component found in your vehicle’s engine management system that controls the fuel’s pressure as it flows to the fuel injectors. Once a regulator starts to fail, it sets off telltale warning signs, which you should heed to avoid a breakdown and costly repairs. But, how does a fuel pressure regulator work, and how do you know when it needs repairs?

How the Fuel Pressure Regulator Works

muscle car engine bayNearly every internal combustion engine has a fuel pressure regulator, which is either a continuous return fuel system in older vehicles or a returnless fuel system, as seen in most modern vehicles. Because the fuel pump delivers more fuel to the engine than it needs, a regulator is needed to control the flow.

In the older system, fuel travels from the gas tank to the fuel rail using the fuel pump. The top section of the regulator is connected by a small vacuum hose, while a large return hose is connected to its side.

Vehicles equipped with a returnless system manage fuel flow without a return line to the fuel tank and with no externally seated regulator. Instead, the regulator resides out of sight inside the tank along with the fuel pump.

Troubling Signs

The fuel pressure regulator usually doesn’t fail without some type of warning. One troubling sign is that the engine won’t operate normally. For instance, it may not turn over immediately, or it could stall when you press the accelerator pedal. You’ll also probably notice a drop in fuel economy, and that’s never a good thing.

If you smell gasoline or your engine backfires when you decelerate — particularly when you lift your foot off the gas pedal — this is a sign that your engine is probably receiving too much fuel. Other indicators that something is wrong include smoke emitting from the tailpipe or gasoline dripping out of it.

Diagnostic Testing

Once your vehicle begins to act strangely, you need to run a diagnostic test to determine the problem’s source.

On vehicles equipped with a continuous return fuel system, connect a fuel pressure gauge and observe pressure levels with the vacuum line connected and again when it’s disconnected. If you notice a variance greater than 8 to 10 PSI, it’s time to replace the regulator.

For cars with a returnless system, a scanner tool will produce an error code to help you diagnose the problem, enabling you to quickly identify the issue and resolve it.

Corrective Action

Ignoring a fuel pressure regulator problem may lead to costly repairs — engine damage is always a possibility the longer you wait. Take corrective action now for peace of mind.

Check out all the engine parts available on NAPA Online or trust one of our 17,000 NAPA Auto Care locations for routine maintenance and repairs. For more information on how a fuel pressure regulator work, chat with a knowledgeable expert at your local NAPA Auto Parts store.

Photos courtesy of Matthew Keegan and Flickr.

Matthew C. Keegan View All

Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.

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