Fuel Pressure Regulator

What is a fuel pressure regulator and where is it located?

In the past, carburetors used to send fuel to the engine for combustion. Today, automobiles use sophisticated fuel injection systems. The fuel pressure regulator (FPR) plays a critical role in a fuel injection system. It is responsible for maintaining the correct fuel pressure so the fuel injectors can disperse the proper amount of fuel needed for combustion. On vehicles with a return-style fuel system, the pressure regulator is typically located on the fuel rails or the injector pod near the injectors. These are also known as inline fuel pressure regulators. Returnless fuel systems will have it built into the fuel filter or the fuel sending unit / pump assembly. These are also referred to sometimes as in-tank fuel pressure regulators. In modern diesel applications, a similar part known as the injector pressure regulator (IPR) is what regulates the oil pressure (oil as in diesel fuel, not engine lubrication).

The fuel pressure regulator contains a diaphragm which a spring pushes against. The spring is set by the manufacturer to be overcome by a certain amount of pressure – the pressure that the fuel injectors need to operate properly. The diaphragm is attached to a valve that opens when that pressure is exceeded and allows fuel to flow into the return line when the fuel pressure exceeds the optimum pressure. This keeps the pressure at the fuel injectors from becoming too high. 

When the engine is idling, it doesn’t need as much fuel pressure as when the vehicle is moving. A vacuum hose attached to the intake manifold helps to reduce the pressure in the fuel regulator at idle. When there is a stronger vacuum in the intake manifold, the vacuum hose pulls the diaphragm in the pressure regulator slightly. This means it takes less pressure for the fuel to overcome the diaphragm. The fuel pressure will increase as the RPM's increase.

How do I know if my fuel pressure regulator needs to be replaced?

Fuel pressure regulators do not fail frequently, but sometimes the high pressure the diaphragm is under can cause wear and damage. When the fuel pressure regulator fails, it will leak gas, resulting in a drop in pressure in the fuel system. A damaged diaphragm may also allow the vacuum hose to suck in gas. These issues can cause engine failure or poor drivability and stumbling at idle, because the engine is not receiving the fuel it needs.

A malfunctioning fuel pressure regulator may leak gasoline into other engine systems. Gas in the vacuum line is a sure sign of a broken fuel pressure regulator. You can also check to see if gas is leaking into your oil. To do this, pull out your oil dipstick. If there is a potent gas smell, then there is a leak. On most applications, a DIY’er can also check pressure in the fuel system with a fuel pressure gauge; many applications have a Schrader valve test port located on the fuel rail. Any deviation from the vehicle specifications indicates a problem with the fuel pressure regulator. A mechanic can perform this procedure as well if needed.

Can I replace a fuel pressure regulator myself?

Replacing a fuel pressure regulator may take a bit of effort and definitely requires some precaution. The fuel regulator already receives fuel at a high pressure, which poses some risk. Before removing the fuel pressure regulator, you’ll want to take the pressure out of the system. You can do this by disconnecting the power from the fuel pump (usually through the fuse) and then idling the engine. This will drop pressure in the fuel lines. Then you can safely remove the fuel pressure regulator. 

Depending on the layout of your engine, the fuel pressure regulator may be fairly easy to access, or it may be underneath other parts — like the intake manifold. You will have to remove any parts that are in the way. Then you can disconnect the fuel lines, the vacuum line, and the electrical harness from the pressure regulator, and unbolt the regulator. To install the new part, reverse the previous steps. 

If your fuel pressure regulator is located in your fuel sending unit, you may have to replace the entire fuel sending unit. On some applications, it may require removal of the gas tank as well.

Need a fuel pressure regulator replacement?

The fuel pressure regulator is what maintains the pressure in your car or truck’s fuel system, so if it has failed it will affect your vehicle's ability to run Therefore you should seek out a fuel pressure regulator replacement as soon as possible when the need arises. At 1A Auto, we carry a large selection of aftermarket fuel pressure regulators - both in-tank and inline - for many makes and models, and at great prices, so that you can get your vehicle back in working order once again.

At 1A Auto, we make shopping for replacement fuel pressure regulators for your car, truck, SUV or van easy - we're here to help you select the right part for your vehicle! Call our customer service toll free at 888-844-3393 if you have any questions about our fuel pressure regulators, warranty, compatibility or to purchase, or you can buy online.