General System Description
INTRODUCTIONThe electronic fuel injection (EFI) system provides a reliable and efficient microprocessor controlled fuel management system.
The function of the system is to supply the exact amount of fuel directly into the inlet manifold according to the prevailing engine operating conditions.
To monitor these conditions, various sensors are fitted to the engine to measure engine parameters. Data from the sensors is received by the electronic control module (ECM) and the ECM will then determine the exact amount of fuel required at any condition.
The ECM having received data from the sensors produces pulses, the length of which will determine the simultaneous open time of each bank of injectors in turn, which will govern the amount of fuel injected.
Changes
An enhanced fuel injection system is incorporated, using a Lucas 14CUX electronic control unit. The system works in the same way, new components being a tune select resistor and a fuel injection fault display unit.
Tune Select Resistor:
Tune Select Resistor--The 14CUX system is used in various markets, but a common ECM is used. To suit individual market requirements a tune select resistor is connected across pins 5 and 27 of the ECM. It is located adjacent to the ECM, and strapped to the EFI cable assembly. The value of the resistor is dependent on the market application.
NOTE: For USA market models the resistor value is 3900 Ohms, wire color, white.
NOTE: Vehicles after VIN 451518 are fitted with a new ECM, Part No. PRC 8747 to replace PRC 7081. This ECM no longer requires the tune select resistor, which is therefore deleted. Fault code 21 is no longer stored by the ECM.
Fuel Injection Fault Display Unit:
Fuel Injection Fault Display Unit--The unit will display the relevant fault code, in addition to the EFI warning light being illuminated.
NOTE: Fault code 59 will NOT be indicated by the EFI warning light.
DESCRIPTION
Electronic Control Module (ECM)--The electronic fuel injection system is controlled by the ECM which is located under the front right hand seat. The control unit is a microprocessor with integrated circuits and components mounted on printed circuit boards. The ECM is connected to the main harness by a 40 pin plug.
Injectors--The eight fuel injectors are fitted between the pressurized fuel rail and inlet manifold. Each injector comprises a solenoid operated needle valve with a movable plunger rigidly attached to the nozzle valve. When the solenoid is energized the plunger is attracted off its seat and allows pressurized fuel into the intake manifold.
Engine Coolant Temperature Sensor--The coolant sensor is located by the front left hand branch of the intake manifold. The sensor provides engine coolant information to the ECM. The ECM on receiving the signal from the sensor will lengthen slightly the time that the injectors are open, and reducing this time as the engine reaches normal operating temperature.
Fuel Temperature Sensor--The fuel temperature sensor is located in the fuel rail forward of the ram housing. The sensor sends fuel temperature data to the ECM. The ECM on receiving the data will adjust the injector open time accordingly to produce good hot starting in high ambient temperatures.
Idle Air Control Valve (IACV)--The IACV is screwed into a housing attached to the rear of the plenum chamber, between the plenum chamber and bulkhead. The IACV has two windings which enable the motor to be energized in both directions thus opening or closing the air valve as required by the ECM.
The IACV will open and allow extra air into the plenum chamber to maintain engine idle speed when the engine is under increased (Electrical and Mechanical) loads.
The IACV will control engine idle speed when the vehicle is stationary.
Lambda Sensors (0xygen Sensors)--The two Lambda sensors are located forward of the catalysts mounted in the exhaust downpipes.
The sensors monitor the oxygen content of the exhaust gases and provide feedback information of the air/fuel ratio to the ECM. Each sensor is heated by an electrical element to improve its response time when the ignition is switched on.
Fuel Pressure Regulator--The fuel pressure regulator is mounted in the fuel rail at the rear of the plenum chamber. The regulator is a mechanical device controlled by plenum chamber vacuum, it ensures that fuel rail pressure is maintained at a constant pressure difference of 2.5 bar (36 psi) above that of the manifold. When pressure exceeds the regulator setting, excess fuel is returned to the fuel tank.
Fuel Pump--The electric fuel pump is located in the fuel tank, and is a self priming wet pump. The motor is immersed in the fuel within the tank.
Air Flow Sensor--The hot-wire air flow sensor is mounted on a bracket attached to the left hand valance, rigidly connected to the air cleaner and by hose to the plenum chamber inlet neck.
The air flow sensor consists of a cast alloy body through which air flows. A proportion of this air flows through a bypass in which two wire elements are situated: one is a sensing wire and the other is a compensating wire. Under the control of an electronic module which is mounted on the air flow sensor body, a small current is passed through the sensing wire to produce a heating effect. The compensating wire is also connected to the module but is not heated. It reacts to the temperature of the air taken in. As engine intake air passes over the wires, a cooling effect takes place.
The electronic module monitors the reaction of the wires in proportion to the air stream and provides output signals in proportion to the air mass flow rate which are compatible with the requirements of the ECM.
Throttle Potentiometer (TPS)--The TPS is mounted on the side of the plenum chamber inlet neck and is directly coupled to the throttle valve shaft.
The potentiometer is a resistive device supplied with a voltage from the ECM. Movement of the throttle pedal causes the throttle valve to open, thus rotating the wiper arm within the potentiometer which in turn varies the resistance in proportion to the valve position. The ECM lengthens the injector open time when it detects a change in output voltage (rising) from the potentiometer.
In addition the ECM will weaken the mixture when it detects the potentiometer output voltage is decreasing under deceleration and will shorten the length of time the injectors are open.
When the throttle is fully open, the ECM will detect the corresponding TPS voltage and will apply full load enrichment. This is a fixed percentage and is independent of temperature. Full load enrichment is also achieved by adjusting the length of the injector open time.
When the throttle is closed, overrun fuel cut off or idle speed control may be facilitated dependant on other inputs to the ECM.
Begining this year, the TPS is self adaptive and no adjustment is necessary.
Road Speed Transducer--The road speed transducer is fitted between the upper and lower speedometer cables. It is mounted on a bracket located on the left hand chassis side member adjacent to the rear engine mounting. The transducer provides road speed data to the ECM. The ECM in turn detects vehicle movement from the road speed input and ensures that idle speed control mode is disengaged. Should the speed transducer fail in service the ECM idle speed control would become erratic.
Inertia Switch--The inertia switch is a mechanically operated switch located under the left hand front seat attached to the seat base rear cross-member.
The switch is normally closed and is in the ignition feed (fuse to fuel pump). In the event of a sudden impact the switch opens, and disconnects the electrical feed to the fuel pump. The switch is reset by pressing down the button.
Relays--The two electronic fuel injection relays are located under the front right hand seat mounted forward of the ECM. The main relay is energized via the ECM when the ignition is switched on and supplies current to the fuel injection system. The fuel pump relay is energized by the ECM which in turn operates the fuel pump to pressurize the fuel system.
Condenser Fans--It should be noted that under high coolant temperatures, when the engine is switched off, the condenser fans will be activated and will run for approximately ten minutes.
Purge Valve--The operation of the charcoal canister purge valve is by the ECM and vents fuel tank vapors to the intake manifold.
EFI Warning Symbol (Check engine warning light)--An EFI warning symbol incorporated into the instrument panel will illuminate when the ECM detects that it cannot maintain correct air/fuel ratio due to a fault in one of the following fuel injection system components:
- Air Flow Sensor
- Lambda Sensor
- Water Temperature Sensor
- Throttle Position Sensor
The symbol will illuminate on initial turn of the ignition key as part of the bulb check feature, and will go out after a few seconds.
If the symbol illuminates when the engine is idling or the vehicle is being driven it indicates a failure of one of the four functions, the vehicle should be driven with care, and the cause rectified. Refer to test procedure for the particular functions. Should one of the functions fail, the vehicle can still be driven due to a limp home feature incorporated into the fuel injection system.