DOHC engine fuel injection system

Elements of the Ford Motorcraft EFI DOHC engine injection system

Design and principle of operation

In the Ford Motorcraft EFI electronic multi-point injection system, fuel supplied at a constant low pressure is directed to four injectors, which inject it into the intake valves. The amount of fuel sprayed is controlled by the opening time of the injectors, determined by the EEC IV electronic control unit, based on the engine speed and the amount of air flow consumed by the engine.

An electric fuel pump, immersed in the tank, pumps fuel constantly through pipelines to the fuel filter, pressure regulator (6), injector manifold (8) and nozzles (10). The pressure regulator maintains a constant pressure for a given vacuum in the intake manifold.


The amount of fuel supplied to each cylinder is controlled by the injector opening time per cylinder cycle.

The EEC IV electronic controller determines this time based on the following signals:

• sensor (5) incoming air temperature;
• engine speed sensor located in the ignition distributor;
• sensor (4) coolant;
• throttle position sensor located in the throttle housing (2);
• automatic transmission shift lever position sensor (in vehicles with automatic transmission);
• air conditioning compressor start sensor (in cars with air conditioning).

On the basis of these signals, the electronic control unit EEC IV ensures the composition of the mixture of fuel and air that is optimal for the given operating conditions of the engine.

In addition, it controls the regulator valve (11) idle, which corrects the idle speed by supplying additional air through the pipeline (3). During engine start, the idle air control valve is open to the maximum.

During idling, its opening changes depending on the need, keeping the engine speed constant.