System Description

Fuel Delivery System:

The fuel system consists of three major subsystems; a fuel storage system, a Feedback Carburetor (FBC) with control system, and a fuel delivery and return system.
FUEL STORAGE
The fuel storage system consists of a fuel tank, a fill spout and filler cap. The filler cap is of a pressure vacuum design to eliminate fuel vapors escaping to the atmosphere. The fill spout contains a restrictor to prevent the addition of leaded fuel to the tank.

FEEDBACK CARBURETOR (FBC) SYSTEM
The Feedback Carburetor (FBC) system is designed to obtain optimum air/fuel mixture during all engine operating modes. The air/fuel ratio is controlled by the Electronic Control Unit (ECU) through the actuation of two solenoid operated valves, the Feedback and Slow cut solenoid valves, which meter air and fuel delivery. The solenoid valves operate at a fixed frequency of 10 hertz. By varying the amount of time the solenoids are energized during each cycle, the ECU can precisely control the air/fuel mixture delivered to the engine in response to signals received from various sensors. The primary difference between the California and Federal systems is in the vacuum sources used to control the high altitude compensation system.

FUEL DELIVERY AND RETURN
The fuel delivery components consist of fuel supply and delivery lines, a mechanical fuel pump and a fuel filter assembly. The fuel return portion of the fuel system consists of lines and couplings and includes the vapor recovery system. The function of the return line is to recover excess fuel vented from the accelerator pump check valve (to relieve excess pump pressure) and return it through the accelerator pump housing, to the fuel tank. The return line is a low pressure part of the fuel system.
The vapor recovery line provides a route for fuel vapors, (both from the fuel tank and the float bowl) to be stored in the charcoal canister, or be evacuated through the purge control system.
Two additional components are included in the vapor recovery system, an overfill limiter and a fuel check valve. The overfill limiter, mounted between the fuel tank the the fuel check valve, limits the amount of pressure or vacuum bled to the fuel tank, through the check valve. The fuel check valve prevents liquid fuel from reaching the evaporative canister in the event of a vehicle rollover.