ourv12

I need to know the fuel pressure with engine running and line hold pressure after engine is shut off.

gedis080

.

Kneale Brownson

Isn't the pressure out of the pump something like 90 psi?

V8QinNJ

6.5 Bar (95.55 PSI).

ourv12

So the fuel pump delivers 95.5 psi to the injectors. The regulator keeps the fuel pressure in the system at what psi at idle? Or what psi at part throttle? I want to check the fuel psi at these two instances. Also want to know the hold pressure after the engine is off.

V8QinNJ

No the pump delivers 6.5 bar to the pressure regluator located on the passenger fuel rail. That pressure regulator drops and maintains the injector pressure at 4 bar. There is a vacuum line connected to the FPR that based on manifold pressure will "adjust" the pressure to meet demand.

If you look at the FPR the fuel line that screws to it is the RETURN to the tank. The Pressure side connects directly to the fuel rail.

Think of it as a release valve.. when the pressure is too high the fuel pushes a spring valve open allowing the excess fuel to flow back to the tank. This is why you will have people say to replace it - because if it fails too much pressure will go directly to the injectors and may flood the cylinder with fuel..

I hope that clears it up for you. Geidis's picture clearly details this...