Fuel Control
An electric in-tank fuel pump supplies fuel through the fuel filter located under the right rear floor pan to the throttle body, maintaining a constant operating pressure. Fuel enters the fuel bowl reservoir of the throttle body through the injector and overflow type fuel pressure regulator. The fuel pump is controlled by the ECU. A ballast resistor attached to the right side of the plenum chamber, reduces fuel pump speed after engine is running. The resistor is by-passed in the "Start" position.
The fuel injector and fuel pressure regulator are integral components of the throttle body. The injector is electronically controlled by the ECU. See Fig 1 .
The fuel pressure regulator is a diaphragm-operated relief valve which maintains fuel pressure of 17.3 psi (1.2 kg/cm2 ). See Fig 2 . Fuel in excess of this pressure is returned to fuel tank by a fuel return line. The regulator is not controlled by the ECU. The regulator's spring chamber is vented to the same pressure as the tip of the injector.
Since fuel pressure at the injector is kept constant, the volume of fuel injected is dependent only on the length of time that the injector is energized. The injection time duration is based on engine operating conditions, which are provided to the ECU by the input sensors. During engine start-up, the injector delivers an extra amount of fuel to aid in starting.