Generator, injectors and ignition 4.4L (Discovery 3)

Contents: Generator ⇩ Nozzles ⇩ Ignition coils ⇩

Generator

The generator has a multifunctional charging voltage regulator (14 V) and a rectifier based on zener diodes.

ECM (engine control unit) controls the electrical system load by PWM (pulse width modulation) -signals and and regulates the generator output power in accordance with the specified load. In addition, the ECM (engine control unit) monitors the battery temperature to determine the generator regulator setting. This parameter is needed to protect the battery from damage. At low battery temperatures, its charging ability is extremely low, and to compensate for this circumstance, the charging voltage must be increased as much as possible, but at high temperatures, the charging voltage must be reduced to prevent excessive gas formation and, as a result, loss of water from the electrolyte.
The alternator circuit contains intelligent controls that reduce the load on the alternator when there is a need to maximize engine torque for other purposes. This control uses three signals to the ECM (engine control unit):

Generator Sensor A measures voltage at the CJB (central mounting box).
The Generator Data Transfer (Alt Com) system transmits the generator voltage setpoint from the ECM (engine control unit) into the generator.
The generator status sensor (Alt Mon) transmits to the ECM (engine control unit) the magnitude of the current in the generator load circuit. In the same data packet in eCm (engine control unit) fault signals are sent. Based on the received CAN messages (engine control unit) sends a request to the instrument cluster to turn on the charging circuit indicator light. For more information, contact Generator (414-02B Generator and Regulator - 4.4L)

Nozzles

There is one injector per engine cylinder (8 in total). Each injector is directly controlled by the ECM. (engine control unit). The injectors are supplied from the fuel rail. The injector supply circuit is part of a closed supply system ("closed" means no backflow in a certain part of the supply system). The fuel pressure regulator, built into the fuel pump located in the fuel tank, maintains a pressure of 4.5 bar in the fuel rail. The serviceability of the injectors is checked by measuring the resistance of the solenoid winding. To check the pressure in the fuel system, a Schrader valve is attached to the left front side of the fuel rail. eCm (engine control unit) monitors the output stage circuits of the injector drive units for electrical faults.

The injector resistance at 20 degrees Celsius should be 13.8 +/- 0.7 ohms. For more information, see Fuel Charging and Controls (303-04B Fuel Charging and Controls - 4.4L)

Ignition coils

The V8 engine has 8 individual ignition coils with a top connector, controlled directly by the ECM (engine control unit). This means that when a sufficient level of inductive charge is reached in the ECM coil (engine control unit) breaks the primary winding circuit of the coil, and a spark is formed between the electrodes of the spark plug. The supply of "positive" voltage to the coil is carried out from a common fuse. Each coil has a power transistor that controls the switching on and off of the primary winding. To turn on the power circuit of each coil, the ECM (engine control unit) sends a control signal. The ignition coil power circuit provides the feedback signal. If a fault occurs in the ignition coil power circuit, the feedback signal is lost and the ECM (engine control unit) records the fault code of the corresponding fault.

To ensure constant discharge energy at the spark plug electrodes, ECM (engine control unit) calculates the closed state period of the primary winding based on the battery voltage and crankshaft speed. This ensures sufficient discharge energy without overloading the primary winding with current, which could cause it to overheat or be damaged.

Ignition timing (spark formation) on each cylinder is determined by the value of several input parameters: