Relieve the fuel system pressure and install a fuel pressure gauge, checking for leakage around the gauge connections when the engine is started. Follow the vacuum hose from the fuel pressure regulator to the intake manifold, disconnecting the hose and installing a vacuum gauge to check for vacuum at the fuel pressure regulator vacuum port; ensure vacuum is present when the engine is started, and if not, check for obstructions. Detach the vacuum hose from the fuel pressure regulator and connect a hand-held vacuum pump, starting the engine to read the fuel pressure gauge with and without vacuum applied; the fuel pressure should decrease as vacuum increases. Reconnect the vacuum hose to the regulator and check the fuel pressure at idle, disconnecting the vacuum hose to observe a jump to the maximum specified pressure; if there is no fluctuation, replace the fuel pressure regulator. If the fuel pressure is low, pinch the fuel return line shut and watch the gauge; if the pressure rises sharply, a faulty pressure regulator is indicated, while no rise suggests a defective
Fuel Pump or restriction in the fuel feed line. If the indicated fuel pressure is too high, stop the engine, relieve the fuel pressure, disconnect the fuel return line, and check for blockage; if there is none, replace the fuel pressure regulator. To replace, relieve the system fuel pressure, detach the cable from the negative battery terminal, remove the vacuum hose and fuel hose from the pressure regulator, unscrew the mounting bolts, and remove the pressure regulator. Installation is the reverse of removal, ensuring a new O-ring is used and lubricated with a light coat of clean engine oil before installation, followed by checking for fuel leaks after the pressure regulator is installed.