Fuel Pressure Regulator

Fuel Pressure Regulator

A fuel pressure regulator is a crucial component of any fuel injection system. Its failure will lead to a variety of engine related problems, including the following:

  • Check engine light is on
  • Increased fuel consumption
  • Black smoke
  • Lack of engine performance
  • Hard engine start or stalling

A faulty fuel pressure regulator may become a source of leaks. This happens when one of its seals or its diaphragm gets damaged. 

A bad fuel regulator may also lead to excessive pressure in the system or, alternatively, its lack, causing the engine to run too rich or lean. 

Fuel pressure regulator basics 

As its name says, the fuel pressure regulator helps to maintain the required pressure of fuel on its way to the fuel injectors. Depending on the type of fuel system, a fuel pressure regulator may vary in design and construction.

Continuous return fuel system

This type of fuel system is common for older vehicles. In such vehicles there is a high-performance fuel pump that supplies fuel from the tank to the fuel rail. As the pump delivers more fuel than it’s usually needed, the excessive fuel returns to the tank via a return line. This is what the fuel pressure regulator is responsible for. It is mounted into the fuel rail and is operated by engine vacuum.

Return-less system

A return-less fuel system can be found in just about any modern vehicle. It has no fuel rail pressure regulator or fuel return line under the hood. This system features a fuel pressure regulator built in the fuel pump assembly placed in the tank, which allows for more precise pressure control and lower emissions.

Some modern return-less systems utilize operational cycles to maintain fuel pressure. They rely on a fuel pressure sensor and are operated by the fuel pump control module or powertrain control module. 

Fuel pressure regulator troubleshooting

A fuel pressure regulator can be inspected using a mechanical gauge, which allows for checking the regulator’s fuel downstream. On some vehicles, a similar job is done using a special scan tool.

On vehicles with a continuous return fuel system, you may check the pressure regulator by taking off its vacuum hose, which should increase the pressure by 8 to 10 PSI. The hose shouldn’t contain any signs of fuel. If it does, you might have a leaking diaphragm.

Unlike a pressure regulator in return fuel systems, a return-less regulator is not repairable. Its failure means a replacement of the pump assembly.