How to Test the Fuel Pressure Regulator on a 1999 Blazer S-10

The fuel pressure regulator on a 1999 Chevy Blazer S-10 is designed to control, through regulation, the fuel pressure present at the fuel injectors. The electric fuel pump in the fuel tank supplies more fuel and pressure than required. A steady 60 pounds per square inch of pressure is all that is needed. The regulator corrects any overpressure condition by allowing the overpressure to be returned to the fuel tank.

Things You'll Need

  • Fuel pressure gauge
  • Rags

Instructions

    • 1

      Lift the hood and locate the fuel pressure regulator on the opposite end of the fuel rail that sits atop the fuel injectors. Look for the fuel inlet line and follow the rail around to the other side of the engine. The regulator is a round diaphragm mechanism with a hose (smaller than the inlet) running back toward the fuel tank.

    • 2

      Remove the cap on the Schrader valve located on the top of the fuel rail and install the fuel pressure gauge.

    • 3

      Start the engine and watch the fuel pressure gauge. Record the fuel pressure. The gauge should read 60 pounds of pressure, regardless of rpm. Performing this check determines whether the problem is with the fuel pump or the pressure regulator. If the fuel pressure is less than 55 pounds per square inch, the fuel pump is kaput. If the pressure is close to 60, grasp the throttle linkage and increase the rpm to 3,000 for one second. Release the throttle. During this time, watch for large fluctuations in the fuel gauge. If the fuel pressure regulator is working properly, there will be no more than a 2-pound differential. Anything more and the regulator is defective.

    • 4

      Allow the engine to idle. Pull the vacuum hose off the regulator and watch the pressure. It should rise sharply, then when the hose is reconnected it should normalize. If this does not happen, the regulator is bad.

    • 5

      Pull the vacuum hose off the regulator again. This is the last check. Check if any fuel is coming out of the regulator. If you see fuel, it is bad. Put your finger over the vacuum port and then smell it for fuel. These regulators are known to blow the diaphragm and leak fuel.

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