Fuel Injection System: Operation: Notes

An on-board electronic engine control (EEC-IV) computer accepts inputs from various engine sensors to compute the required fuel flow rate necessary to maintain a prescribed air/fuel ratio throughout the entire engine operational range. The computer then sends a command to the fuel injectors to meter the required quantity of fuel.

The EEC-IV engine control system automatically senses and compensates for changes in altitude (sea level to mountains) and will also permit push starting the vehicle, if necessary.

The fuel delivery subsystem consists of an in-tank low-pressure pump, and a high pressure chassis-mounted electric fuel pump. Fuel drawn from the fuel tank passes through a filter before entering the low pressure pump. The fuel is filtered again as it leaves the high pressure pump on its way to the pulse damper and fuel supply manifold. The pulse damper smooths the pressure variations generated by the opening and closing of the fuel injectors.

The fuel supply manifold assembly incorporates electronic fuel injectors directly above each of the engine's 4 intake ports. When energized, the injectors spray a metered quantity of fuel into the intake air stream. A constant fuel pressure drop is maintained across the injector nozzles by a pressure regulator. The regulator is connected in series with, and downstream from the fuel injectors. Excess fuel supplied by the pump, but not required by the engine, passes through the regulator and returns to the fuel tank through a fuel return line.

Two injectors are energized simultaneously, once every crankshaft revolution. The period of time that the injectors are energized (injector "on time" or pulse width) is controlled by the vehicle's Electronic Engine Control (EEC) computer. Air entering the engine is measured by a vane airflow meter located between the air cleaner and the turbocharger. The airflow is then compressed by the turbocharger before introduction into the intake manifold. This airflow information along with input from various other engine sensors is used to compute the required fuel flow rate.