The injection system supplies fuel required for combustion at constant pressure to the injectors. Fuel is metered and injected into the intake manifold according to signals from the Engine Control Unit (ECU). In general, the system consists of the fuel pump, fuel filters, delivery pipe, pulsation damper, pressure regulator, fuel injectors, fuel pump switch and circuit opening relay. On the 1988-89 turbocharged 323 (with 4WD) and MX-6 (with 4WS), there is also a fuel transfer pump built into the system.
The fuel pump is mounted inside the fuel tank to reduce the operating noise that is characteristic of electric fuel pumps. The fuel injectors are supplied with direct battery voltage by the main relay, while the ECU varies ground for operation. Fuel injector connectors on these systems are color coded to distinguish turbocharged from non-turbocharged injectors.