How do you test the fuel pressure regulator on a 1987 Volvo 740 gle non turbo?

To test the fuel pressure regulator on a 1987 Volvo 740 GLE non-turbo, first, relieve the fuel system pressure by removing the fuel pump fuse and running the engine until it stalls. Then, disconnect the vacuum line from the regulator and check for fuel presence in the hose, which indicates a faulty regulator. Next, connect a fuel pressure gauge to the fuel rail's test port and compare the reading to the manufacturer's specifications; it should typically be around 36-42 psi. If the pressure is outside this range or the regulator leaks fuel, it needs replacement.