Fuel System and Injectors

Once the ignition is turned on the EEC IV applies 12v to the fuel pump relay which in turn switches on the fuel pump. The fule pump relay is feed from fuse 'P' and when energised by a signal from EEC pin 22 turns the pump on.

Fuel is then sent, via a pressure regulator (swirl pot) and filter to the fuel rail and onto the injectors. The swirl pot ensures a constant supply of fuel even under harsh cornering or braking conditions minimising the chances of fuel pump and engine failure due to fuel starvation.

The fuel rail functions as a holding reservior and once the injectors are pulsed open then fuel will flow into the cylinder. The quantitiy of fuel injected is based on the length of the opening pulse from the EEC.

Each injector is not pulsed individually but only once at each revolution of the crankshaft.

The fuel injector is a magnetically operated solenoid valve and has a two pin plug atthe top of the unit.


The EEC IV electrical fuel system is controlled by a main injection relay ad a fuel pump relay.

Relay pin numbering is standard configuation and shown below.

Standard Relay Connections

Operation : Once the ignition is turned on a voltage supply from the ignition switch is applied to the main relay terminal 86. This terminal is connected to the chassis via the inductor winding and out to earth on terminal 85. When energised contacts 87 and 30 are then short circuit and in turn apply 12v to the terminal 86 of the fuel pump relay, injectors and various other actuators.

When the ignition is turned on the EEC briefly applies an earth to pin 22 which briefly energises the fuel pump relay turning the fuel pump on. After a second the EEC open circuits this and the fuel pump stops. This 1 second running allows pressure to build up in the fuel pressure lines allowing easier starting.

The fuel pump relay remains open circuit until the engine turns over and a signal is received from the engine speed sensor, the relay will then energise and the fuel pump will run normally.

Voltage Tables

(NBV = Nominal Battery Voltage)

Fuel System Tables 1 - Main Relay


Fuel System Tables 2 - Fuel Pump Relay

The following diagram shows the two conditions that can exist for the fuel system; with the ignition off and on.

Click on the picture to toggle size.

Fuel System Conditions


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