Fuel Supply System

Fig. 2 Digital electronic fuel injection fuel supply system:

Fig. 3 Digital electronic fuel injection fuel pressure regulator:

Fig. 4 Digital electronic fuel injection fuel injector:

The fuel supply system components, Fig. 2, provide fuel at the correct pressure for metering by the injectors into the throttle bores. The pressure regulator controls fuel pressure to a nominal 10.5 psi across the injectors. The fuel supply system consists of a fuel tank mounted electric pump, a full-flow fuel filter mounted on a vehicle frame, a fuel pressure regulator integral with the throttle body, fuel supply and fuel return lines and two fuel injectors. The timing and amount of fuel supplied is controlled by the ECM.
An electric motor driven twin turbine type pump, integral with the fuel tank float unit, provides fuel at a positive pressure to the throttle body and fuel pressure regulator. The pump is specific for DEFI application and is not serviceable; however the pump may be serviced separately from the fuel gage unit.
Fuel pump operation is controlled by the fuel pump relay, located in the relay center. Operation of the relay is controlled by a signal from the ECM. The fuel pump circuit is protected by a 10 amp fuse located in the fuse block. The ECM activates the pump with the ignition ON or START. However, if the engine is not cranked within one second after ignition is turned on, the ECM signal is removed and the pump is deactivated.
Fuel is pumped from the fuel tank through the supply line into the filter to the throttle body and pressure regulator. The injections supply fuel to the engine in precisely timed bursts as a result of electrical signals from the ECM. Excess fuel is returned to the fuel tank through the fuel return line.
The fuel tank incorporates a reservoir directly below the sending unit-in-tank pump assembly. The ``bath tub'' shaped reservoir is used to ensure a constant supply of fuel for the in-tank pump even at low fuel level and severe maneuvering conditions.
The Fuel Filter consists of a casing with an internal paper filter element capable of filtering foreign particles down to the 10 micron size. The filter element is a throw away type and should be replaced when recommended. The filter is mounted to the frame near the left rear wheel.
The fuel pressure regulator Fig. 3, is integral with the throttle body. The valve, which regulates pressure, is a diaphragm-operated relief valve in which one side of the valve senses fuel pressure and the other side is exposed to atmospheric pressure. Nominal pressure is established by the pre-load spring. Constant pressure drop across the injectors is maintained by referencing to the ambient pressure at the throttle body. Fuel in excess of that is used to maintain constant pressure by the engine is returned through the fuel return line to the fuel tank. The regulator is not serviced separately from the fuel body assembly.
During normal operation, the two fuel injectors, Fig. 4, are actuated alternately by the ECM and are used to meter and direct the atomized fuel into the throttle bores above the throttle blades. During cranking, both injectors are actuated simultaneously to aid starting.
The injector body contains a solenoid. The plunger or core piece is pulled upward by the solenoid allowing the spring loaded ball valve to come off the valve seat, which then allows fuel through to the atomizer/spray nozzle. Injectors may be replaced individually.
A 3/8 inch fuel delivery line is routed along the left frame side rail between the fuel pump/sending unit assembly and the throttle body. A braided stainless steel covered Teflon hose is used to connect the metal fuel line to the fuel line on the engine to provide high system integrity and protection against abrasion.
The fuel return line is 5/16 inch in diameter and is routed along the right frame side rail. Flexible connection in this line is also by braided stainless steel covered teflon hose at the engine to frame junction.