To check the fuel pump output and pressure, first ensure that there is enough fuel in the tank and relieve the fuel pressure. Then, install a fuel pressure gauge onto the fuel lines or fuel rail using the appropriate adapter fitting. With the ignition switch on but the engine not running, observe the fuel pump running for about two seconds and note the reading on the gauge. After the pump stops running, the pressure should remain steady within the specified range. If the pump does not turn on, check the fuel pump's electrical circuits. Start the engine and let it idle at normal operating temperature, and the pressure should be slightly lower. If all pressure readings are within specifications, the system is functioning properly. If the pressure did not drop after starting the engine, apply vacuum to the pressure regulator. If the pressure drops, repair the vacuum source; if not, replace the regulator. If the fuel pressure is not within specifications, check for vacuum to the pressure regulator and for a pinched or clogged fuel return hose or line. If these are okay, replace the pressure regulator. If the pressure is still low with the fuel return line restricted, the fuel pump may be faulty. After testing, relieve the fuel pressure and remove the gauge. For the fuel pump electrical circuit check, listen for a whirring sound at the fuel filler neck opening when the ignition key is turned on. If no sound is heard, check the fuel pump fuse. If the fuse is okay, remove the fuel pump relay and check for battery voltage to the relay connector with the ignition key off and on. If there is no voltage, check the fuel pump fuse and wiring circuit. If voltage is present, check the relay and then check for battery voltage at the fuel pump connector. If there is no voltage, check for an open circuit between the fuel pump and the relay. If there is power at the fuel pump connector and the pump still does not work, try bypassing the fuel pump circuit and powering it up with battery voltage. Additionally, check the oil pressure and oil pressure switch if the fuel pump fails to operate.
