Lucas 14CUX System (3.9L & 4.2L V8)

The "Hot Wire" Multiport fuel injection system derives its name from the mass air flow sensor which uses one cold wire and one electrically heated wire to measure the volume of air entering the engine.

The function of the system is to supply the exact amount of fuel directly into the intake 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 Engine Control Module (ECM), 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.

Electronic fuel injection system is controlled by ECM which is located under right front seat (1990-1992 model year) or on the right side, behind "A" pillar trim panel (1993-Early 1995 model year). ECM is a microprocessor with integrated circuits and components mounted on printed circuit boards. ECM is connected to main harness by a 40-pin connector.

Since 1990 model year, vehicles have an enhanced fuel injection system, using a Lucas 14CUX electronic control unit. The system is a development of 14CU system introduced on 3.9 liter vehicles in 1989. See appropriate THEORY & OPERATION article. The system works in same way, new components being a tune select resistor and a fault code display unit.

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 No. 5 and No. 27 of ECM. It is located adjacent to ECM, and strapped to EFI cable assembly. See Fig 1 . The value of resistor is dependent on market application.

NOTE: On 1990 US models, the resistor value is 3900 Ohms (with White wire).

NOTE: On US models, vehicles produced after VIN No. 451518 are fitted with a new ECM (PRC 8747) to replace PRC 7081. This ECM no longer requires tune select resistor, which is therefore deleted. Fault code 21 is no longer stored by ECM.

NOTE: Fault code 59 will NOT be indicated by EFI warning light.

On 1991-Early 1995 models, if vehicle is equipped with a resistor, the resistor values are as follows:

RED wire (180 ohms) - Australia and rest of world
GREEN wire (470 Ohms) - European (Non-Catalyst)
WHITE wire (3009 Ohms) - European (Catalyst)
YELLOW wire (910 Ohms) - Saudi Arabia (Non-Catalyst)

The tune select resistor receives a 5 volt signal from the ECM. The opposite terminal of the tune select resistor is grounded at all times. The tune select resistor causes the 5 volt signal read at the ECM terminal No. 5 to decrease. The ECM determines how the engine should perform based on the amount of voltage at terminal No. 5.

1990 model year vehicles have a fault code display unit which is located underneath right hand front seat, adjacent to ECM. See Fig 2 . The unit will display relevant fault code, in addition to EFI waning light being illuminated.

The diagnostic equipment for checking out 14CUX system is same as that used for 14CU, with addition of two 14CUX memory cards (Lucas 60601379) for Hand Held Tester.

Fig 1: Identifying Tune Select Resistor (Lucas 14CUX System)

Courtesy of LAND ROVER NORTH AMERICA, INC.

Fig 2: Identifying Fault Code Display Unit (Lucas 14CUX System)

Courtesy of LAND ROVER NORTH AMERICA, INC.