Land Rover Defender V8i Electrical Library Rover Manual
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DESCRIPTION AND OPERATION 4.10 DEFENDER V8i IGNITION SYSTEM The ignition system utilises a direct ignition system (DIS) negating the need for a distributor. The system comprises 4 double ended coils operating the wasted spark principle. The circuit to each coil is controlled by the ECM. When a coil fires, a spark is produced in two cylinders, however, as the resistance is higher in the cylinder on the compression stroke, more spark energy is dissipated in this cylinder. The ECM determines the optimum ignition timing based on signals from the following sensors: ·Crankshaft position (CKP) sensor - engine speed and crankshaft position ·Camshaft position (CMP) sensor - camshaft position ·Intake air temperature (IAT) sensor - inlet air temperature ·Knock sensors - engine vibration, detonation The engine management system uses no centrifugal or vacuum advance, timing is controlled entirely by the ECM. Crankshaft position (CKP) sensor The CKP sensor signal is used as the basis for ignition timing. It informs the ECM that the engine is turning, the speed the engine is turning and position of the engine in its cycle. The sensor uses the principle of magnetic induction to generate the signal. A reluctor ring, attached to the engine flywheel, has a series of teeth spaced at 10°intervals, with one tooth missing at 20°after TDC. The reluctor ring rotates with the flywheel, in close proximity to the CKP sensor. As each tooth of the reluctor ring passes the sensor, it disturbs the magnetic field of the sensor and a voltage is induced in the sensor coil. The ECM calculates engine speed by counting pulses per second from the CKP sensor. Engine position is calculated by counting pulses after the missing pulse.
DESCRIPTION AND OPERATION DEFENDER V8i4.11 Camshaft position (CMP) sensor The CMP sensor is used in conjunction with the CKP sensor to inform the ECM of the position of the engine in the 4 stroke cycle. Using the CKP sensor alone, the ECM is unable to determine whether a cylinder is on its compression stroke or exhaust stroke. The sensor uses the principle of magnetic induction to generate the signal. The cam wheel has four gaps, one smaller than the others, which pass in close proximity to the CMP sensor as the camshaft rotates. The lobes disturb the magnetic field of the sensor and induce a voltage in the sensor coil. In the event of a sensor failure, the ECM will continue to operate normal ignition timing and sequential fuel injection using the CKP sensor signal. The sequential fuel injection may be 180°out of phase. Engine knock detection and correction will be disabled. Inlet air temperature (IAT) sensor The basis of the IAT sensor is a temperature dependent resistive metal strip. The resistance of the metal strip varies considerably with temperature. When an inlet temperature of 55°C or higher is detected, the ECM retards the ignition timing . If the sensor fails, the ECM assumes an inlet temperature or 50°C. Knock sensor The knock sensor is a piezo-electronic accelerometer, which produces an electronic signal related to the vibration of the engine. A knock sensor is located in each bank of cylinders. The signal from each knock sensor is transmitted to the ECM. The ECM is able to filter out normal engine vibrations and detect vibrations induced by engine knock.
DESCRIPTION AND OPERATION 4.12 DEFENDER V8i Using the signal from the knock sensor in conjunction with the CKP and CMP signals enables the ECM to identify which cylinder is producing the knock and hence retard the ignition timing of that cylinder only. The ignition timing of the cylinder producing the knock is retarded until the knock disappears. The ECM then advances the ignition timing to find the optimum advance angle for that cylinder. The ECM is able to perform a similar function for each of the 8 cylinders simultaneously. It is therefore possible for all 8 cylinders to have different advance angles at any one time. FUELLING SYSTEM Engine fuelling is by a fully sequential, electronic fuel injection system, controlled by the ECM. The ECM determines the timing and quantity of fuel to be injected based on information received from the following sensors. ·Crankshaft position (CKP) sensor - engine speed and crankshaft position ·Camshaft position (CMP) sensor - camshaft position ·Mass air flow (MAF) sensor - quantity of air entering the engine ·Throttle position (TP) sensor - position of throttle and rate of change of throttle ·Engine coolant temperature (ECT) sensor - engine coolant temperature ·Fuel temperature sensor - temperature of fuel rail ·Heated oxygen sensor (HO2S) - oxygen content of exhaust Crankshaft position (CKP) sensor The CKP sensor signal is used as the basis for fuel injection timing. It informs the GEMS that the engine is turning, the speed the engine is turning and position of the engine in the cycle. The sensor uses the principle of magnetic induction to generate the signal. A reluctor ring, attached to the engine flywheel, has a series of teeth spaced at 10°intervals, with one tooth missing at 20°after TDC. The reluctor ring rotates with the engine, in close proximity to the CKP sensor. As each tooth of the reluctor ring passes the sensor, it disturbs the magnetic field of the sensor and a voltage is induced in the sensor coil. The ECM calculates engine speed by counting pulses per second from the CKP sensor. Engine position is calculated by counting pulses after the missing pulse.
DESCRIPTION AND OPERATION DEFENDER V8i4.13 Camshaft position (CMP) sensor The CMP sensor is used in conjunction with the CKP sensor to inform the ECM of the position of the engine in the 4 stroke cycle. Using the CKP sensor alone, the ECM is unable to determine whether a cylinder is on its compression or exhaust stroke. The sensor uses the principle of magnetic induction to generate the signal. The cam wheel has four lobes which pass in close proximity to the CMP sensor as the camshaft rotates. The lobes disturb the magnetic field of the sensor and induce a voltage in the sensor coil. In the event of a sensor failure, the ECM will continue to operate sequential fuel injection using the CKP sensor signal. It is possible that the injection timing will be one engine revolution out of sequence. Mass air flow (MAF) sensor The MAF sensor is used to measure the quantity of air being drawn into the engine and hence give an indication of the quantity of fuel to be injected to provide a stoichiometric mixture strength. The MAF sensor is an anemometer located in the inlet air flow and consisting of two wires, one heated and one not. The non heated wire is at ambient temperature and has a resistance which is used as a reference. The heated wire is maintained at a constant temperature difference above the non heated wire. As air flows over the heated wire, current is applied to the wire to maintain the temperature difference, the faster the air flow, the greater the cooling effect and the greater the current required to maintain the temperature difference. The current supplied to the hot wire is converted to a voltage signal and sent to the ECM. The ECM uses the voltage signal to calculate the quantity of air being drawn into the engine. If the sensor fails, the ECM calculates a value dependent on throttle position, engine speed and air temperature.
DESCRIPTION AND OPERATION 4.14 DEFENDER V8i Throttle position (TP) sensor The TP sensor measures the angle of throttle opening and the rate of change of throttle position. The angle of throttle opening gives an indication of the quantity of air being drawn into the engine. The rate of change of throttle angle gives an indication of rate of acceleration demanded. The sensor is a rotary variable resistor mounted to the throttle butterfly spindle giving an output of 0 to 5 volts. Engine coolant temperature (ECT) sensor The coolant temperature sensor measures the temperature of the engine coolant. The signal from the coolant sensor is used by the ECM to adjust the fuelling mixture. The engine requires a richer mixture at lower temperatures. The sensor relies on a temperature dependent resistive metal strip. The resistance of the metal strip varies considerably with temperature and is immersed in the engine coolant. If the sensor fails, the ECM assumes an engine coolant figure of 80°C. The fault could be noticable during the engine warm up period. Fuel temperature sensor The fuel temperature sensor measures the temperature of the fuel rail. The signal from the sensor gives the ECM a warning of fuel vapourisation and the possibility of bubbles forming in the injectors. If the ECM receives a high fuel temperature signal during starting, the fuel injector opening period is increased to clear any vapourisation bubbles from the injectors and correct the fuelling. When the engine is running, fuel circulation from the fuel tank keeps the fuel rail cool and flushes away any bubbles.
DESCRIPTION AND OPERATION DEFENDER V8i4.15 Heated oxygen sensor (HO2S) 2 HO2Ss are fitted to the vehicle, 1 before each catalyst. A HO2S comprises a titanium metal sensor surrounded by a gas permeable ceramic coating. Oxygen permeating the ceramic coating reacts with the titanium wire, altering its resistance. The resistance of the sensor is directly related to the quantity of oxygen around the sensor. The HO2S does not function correctly until it reaches a temperature of approximately 300°C and so a heating element is incorporated into the sensor to provide rapid warm up after a cold start. The signals from the HO2Ss are used by the ECM to correct the fuelling to each bank of cylinders independently. The 2 sensors measure the oxygen content of the gasses exhausted from the engine, indicating a rich or weak mixture strength. The ECM alters the pulse width of the injectors to correct the mixture strength and achieve a stoichiometric air/fuel ratio. Injectors The fuel injection system has 8 fuel injectors, 1 for each cylinder. Each injector comprises a solenoid with a needle valve held in position by a spring. The route to ground for the solenoid is controlled by the ECM. When energised, the solenoid lifts the needle valve from its seat and pressurised fuel from the fuel rail flows through the injector. The injector orifice is shaped to produce a fine spray of fuel which aids combustion.
DESCRIPTION AND OPERATION 4.16 DEFENDER V8i Fuel pressure regulator The fuel pressure regulator is a mechanical device mounted to the fuel rail. Its purpose is to control the fuel rail pressure with respect to the inlet manifold depression. The fuel rail pressure must be reduced at high manifold depressions to avoid excess fuel being drawn through the injector nozzles. The fuel regulator contains a spring loaded diaphragm valve with pressurised fuel on one side of the diaphragm and manifold vacuum acting on the other. When fuel rail pressure, assisted by manifold depression, overcomes the diaphragm spring load , fuel flows past the diaphragm valve to the fuel tank, reducing fuel rail pressure. With manifold depression low, during hard acceleration, the fuel rail pressure must be high to overcome the diaphragm spring load. With manifold depression low, during coast down, the vacuum acting on the diaphragm valve acts against the spring load and a lower fuel rail pressure lifts the valve from its seat. Idle air control valve (IACV) Engine idle speed is maintained by the IACV, connected to the stepper motor and controlled by the ECM. With the throttle butterfly fully closed, a small quantity of air is able to by-pass the throttle butterfly via the base idle passage. The ECM monitors engine speed and load via sensors around the engine. Should extra air be required to maintain a steady idle speed, the ECM signals the stepper motor to operate a number of steps and open the IACV to allow air through the throttle by-pass. The stepper motor operates over a range of 180 steps with the IACV fully open at 0 steps and fully closed at 180 steps.
DESCRIPTION AND OPERATION DEFENDER V8i4.17 Purge valve The vehicle is equipped with an evaporative emission control system designed to prevent vapour loss from the fuel tank. Fuel tank vapour is passed through a charcoal canister which traps fuel vapour. The vapours trapped by the charcoal canister is drawn in to the engine through the purge valve and burnt in the combustion chamber. The ECM controls the opening of the purge valve to allow venting of the charcoal canister. The ECM pulses the purge valve open for short periods when the engine has reached normal operating temperature and is turning at a speed over 1700 rpm. This is done to ensure that the fuelling of the engine is not adversely affected during warm up or at idle. During purge valve operation, the ECM monitors HO2S signals. If opening the purge valve causes the HO2S signal to indicate a leaner mixture, the ECM assumes that the charcoal canister is empty. When the charcoal canister is monitored to be empty, the purge valve is opened to prevent a build up of fuel vapour in the canister. With the purge valve open, unmetered air is drawn into the engine through the charcoal canister. The ECM uses the signal from the HO2Ss to corrects the fuelling. Inertia switch Power to the fuel pump is supplied via the inertia switch. In the event of extreme deceleration, as would be experienced in a collision, the inertia switch trips, isolating electrical supply from the fuel pump. The switch is reset by pressing the rubber button on top of the switch.
DESCRIPTION AND OPERATION 4.18 DEFENDER V8i DIAGNOSTIC SOCKET DESCRIPTION The diagnostic socket is located below the passenger compartment fuse box. The connector is constructed to ISO standard and allows the attachment of TestBook or any other ISO standard scantool. The diagnostic socket allows diagnostic information stored in any of the vehicles ECUs to be retrieved. It also allows engine tuning and fault diagnosis to be carried out via the engine control module (ECM). OPERATION Feed from the positive battery terminal is connected to the engine compartment fuse box (C1217-1) by a brown wire. A constant battery feed is provided to the diagnostic socket (C40-16) by fuse 4 (C573-1) of the engine compartment fuse box on a purple wire. An earth is provided for the socket (C40-4) on a black wire. To allow TestBook to interact with the Alarm ECU, the diagnostic socket (C40-8) is connected to the ECU (C61-17) by an orange/light green wire. To interact with the ECM, 2 pins are set aside (C40-7 & C40-15). The ECM is connected to the diagnostic socket by white/pink (C636-20) and white/light green wires (C636-23).
DESCRIPTION AND OPERATION DEFENDER V8i4.19 AIR CONDITIONING DESCRIPTION The air conditioning (A/C) system fitted to the Defender 50LE operates independently of the standard heating and ventilation system. Controlled by 2 switches mounted in the centre of the fascia, the A/C system will only operate when the engine is running and the blower control is in at least position 1. The blower control is a 3 position switch, and works in conjunction with the temperature control. Temperature control is by a variable resistor. The cooled and dehumidified air produced by the A/C system is directed through vents located in the lower fascia bezel. The A/C system can be used in conjunction with the standard heating and ventilation system. By combining the two separate systems, virtually any required interior condition can be met. OPERATION Feed from the positive battery terminal is connected to the engine compartment fuse box (C1217-1) by a brown wire. Current flows across fusible link 1 and fusible link 2, which are connected in series. From fusible link 2 (C570-1), current flows to fuse 15 and 16 (C581-5) of the passenger compartment fuse box on a brown/purple wire. Fuses 15 and 16 are connected in parallel. Fuse 15 (C581-10) supplies a feed to the blower relay switch (C817-30) on a brown/slate then purple/slate wire. Fuse 16 (C581-12) supplies a feed to both the condenser fan relay switch (C1212-30) on a brown/white wire, and the compressor clutch relay switch (C1213-30), also on a brown/white wire. When the ignition switch is turned to position II, current is allowed to flow from the ignition switch (C90-1) to fuse 17 (C581-13) of the engine compartment fuse box on a white wire.