Happy Holiday to all in US

Can someone explain the device on the fuel rail that has 2 vac lines attached to it (86 SIII) Picture below

One line goes to fuel pressure regulator and other line to intake manifold

Also could you also explain the general operation of the regulator and this device in maintaining fuel pressure

Thanks

 

Fuel temperature switch.

When the fuel reaches xxx-temp (157ºF I think....but might be wrong) this device dumps the vacuum signal to the regulator. In turn, this increases fuel pressure. The idea being that any fuel vaporization in the fuel rail will be elimination by increased fuel pressure. This assists in hot starting under very hot conditions. Early Ser III cars did not have this feature. It was originally sold as an add-on kit but was later incorporated into regular production.

The fuel pressure regulator controls fuel pressure by letting xxx-amount of fuel flow into the return line to the tanks. More fuel returned to the tanks = less fuel pressure in the rail. This is done in accordance to manifold vacuum. Higher vacuum yields less fuel pressure and vice versa. The actual measured fuel pressure doesn't vary all that much; maybe 4-5 psi. Just enough to control the pressure drop across the injector.

Cheers
DD

 

Perfect! As always Doug... many thanks to you

Randy