1. Disconnect and plug the fuel pressure regulator vacuum hose. Connect a hand vacuum pump to the regulator. Start the engine and read the fuel pressure without regulator vacuum. Create a negative pressure in the regulator and read the fuel pressure again. As the vacuum at the regulator increases, the fuel pressure should decrease. Compare the readings with those given in subsection 5.2.1.
2. Attach the vacuum hose to the regulator and check the fuel pressure at idle, Compare the readings with the normative ones.
3. Disconnect the hose and read the pressure again - as soon as the hose is disconnected, the pressure should rise abruptly to the upper limit. If the fuel pressure at idle with the hose disconnected is too high, measure the vacuum on the vacuum hose with a vacuum gauge. If the vacuum gauge does not show anything, then check the tightness of the suction manifold and surge chamber.
4. On early models, the vacuum valve of the regulator is triggered by a contact temperature sensor, on later models it is controlled by a processor unit. Checking the vacuum valve is carried out in a car service.
5. If the fuel pressure is too low, pinch the return hose. If the pressure does not increase, then the pump is faulty or the fuel line is clogged. If the pressure rises sharply, replace the pressure regulator.
6. If the fuel pressure is too high, then decompress the system, disconnect the fuel return line and purge it. If the fuel return line is not clogged, replace the pressure regulator.
7. If the pressure behavior differs from that described in point 2, then replace the pressure regulator.
8. Carefully remove the pressure gauge.
9. Wrap the fitting of the fuel distributor after replacing the gaskets.
10. Wipe up spilled gasoline.
11. Start the engine and check for fuel leaks.