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Re: low fuel pressure
Fuel in the line is under pressure from the pump, past the injectors and up to the regulator outlet. Spring pressure on the regulator diaphragm closes the outlet passage inside the regulator allowing fuel pressure to build. When fuel pressure overcomes spring pressure, the regulator opens the passage and the excess is sent back to the fuel tank through the return line.
Key in the RUN position, engine off, fuel pump running, pressure must be 60psi to 66psi and remain above 55psi for 3 to 5 minutes after the fuel pump shuts off. If fuel pressure drops below 55psi, one of the causes could be a leaking fuel pressure regulator. The fuel pressure regulator is a very simple design and has very few problems. Most of the time when regulators are replaced, it's a result of mis-diagnosis.
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