To perform the fuel pressure test, you'll need a fuel pressure gauge capable of measuring high fuel pressure and an adapter set for the fuel injection system being tested. Check there's adequate fuel in the tank. Ensure the fuel pump runs by removing the fuel filler cap, turning the ignition key to the On position, and listening for a whirring sound from the fuel filler opening. Relieve the fuel system pressure, install a fuel pressure gauge and adapter between the fuel filter and the rear fuel rail. With the ignition On and the air conditioning Off, the fuel pump should run, and pressure should register on the gauge. Start the engine and idle, then disconnect the vacuum hose from the
Fuel Pressure Regulator to see if the pressure increases. If the pressure isn't within specifications, check for vacuum to the fuel pressure regulator, for a pinched or clogged fuel return hose, or replace the regulator. Monitor the pressure on the gauge with the engine Off and the ignition On; if the pressure changes too much, an injector may be leaking or the in-tank fuel pump leakdown valve might be faulty. After testing, relieve the fuel pressure and remove the gauge. If the pump doesn't turn on, check the fuel pump fuse. If fuses are intact, check for battery voltage at the fuel pump harness connector and for continuity to ground. If there's no voltage, check the fuel pump relay. If the relay functions, probe the relay connector with a test light after turning the ignition On; the light should illuminate briefly, indicating the ground circuit from the PCM works. If the relay connector has the correct signals, check the relay-to-fuel pump harness circuit for issues.