Range Rover. Manual — part 76
BMW DIESEL
9
DESCRIPTION AND OPERATION
Fuel injection pump (FIP)
The FIP is of the vane-type and is chain driven from
the front end of the crankshaft. Fuel delivery from the
FIP to the injectors is regulated by the movement of a
control spool. Movement of the control spool
increases or decreases the fuel delivery rate to meet
engine operating requirements.
The FIP houses the following items that either send
signals to the ECM, or responds to signals sent from
the ECM:
Fuel quantity servo unit
Moves the control spool to regulate the amount of fuel
delivered to injectors.
Servo unit potentiometer
Used by the control unit to calculate the position of the
control spool.
Injection timing device
Regulates pump speed dependent on internal pump
pressure.
Fuel temperature sensor
Monitors fuel temperature.
Stop solenoid
Cuts fuel delivery to the injectors when de-energised.
These items have been previously described in this
section -
See Input devices or Output devices as
applicable.
1. Rotary potentiometer
2. Quantity control servo unit
3. Stop solenoid
4. Injection timing device solenoid valve
5. Control spool
6. Timing device plunger
7. Drive shaft
8. Fuel temperature sensor
19
FUEL SYSTEM
NEW RANGE ROVER
10
DESCRIPTION AND OPERATION
OPERATION
General
The digital diesel electronics system (DDE) facilitates
exact control of injection quantity and injection timing
under all operating conditions. As a result, fuel
consumption and exhaust emissions are kept to a
minimum.
Malfunctions
If a fault occurs in any of the following circuits:
manifold absolute pressure sensor, fuel temperature
sensor or coolant temperature sensor, the ECM will
provide substitute values. In the case of a faulty
throttle position sensor, start of injection sensor or
injection timing device, the engine will run at a
reduced performance level.
If the servo unit potentiometer or servo unit fails, the
injection system is deactivated. The engine shuts
down as a result.
Injection timing (Start of Injection) control
The start of injection is controlled by the injection
timing device in the injection pump. A solenoid valve
modulates the internal pump pressure on one side of
the system so that a defined start of injection is set.
When no power is applied, the solenoid valve is
closed, resulting in advanced injection timing (start of
injection).
Injection quantity control
Injection quantity control is achieved by the quantity
servo control unit in the injection pump. The servo
acts on the pump control spool to vary the effective
stroke of the pump piston (injection quantity). The
position of the control spool is signalled back via the
servo potentiometer to the ECM. The ECM compares
the actual value with the nominal value and, if
necessary, adjustment is carried out until the nominal
injection quantity value is achieved. The servo control
unit is set to zero delivery when no power is applied.
Start control
To determine the quantity of fuel to inject during
starting, the ECM uses signals from the coolant
temperature sensor, fuel temperature sensor,
crankshaft position sensor and throttle position
sensor.
Engine speed control
After starting, an idle speed control function cuts in
after a certain engine speed threshold has been
exceeded. This is calculated by the ECM dependent
on the coolant temperature and the active loads. The
idle speed can be adjusted by means of TestBook.
The maximum engine speed is limited by the ECM by
reducing the injection quantity.
Running stability control and jolt damping
The running stability control system is used for engine
speed stabilization when idling. Controlled injection
quantity correction counteracts the irregularities which
occur in the individual cylinders as the result of
dispersion of the injected fuel quantity.
In the case of spontaneous change in the position of
the accelerator pedal or a sudden change in the
driving resistance, vibrations occur which, in
conjunction with the control frequency of the injection
hydraulics, can result in jolts and jerks.
On the basis of segment-by-segment angle evaluation
in the input sequence, the engine speed signals
provide the information which is used for corrective
control (rotation irregularities) in the quantity servo
control unit. The prerequisite for this function is the
input of the vehicle speed signal.
Exhaust emission limitation and overheating
protection
At high ambient air temperatures and at increasing
altitude, the full load quantity is reduced in order to
limit exhaust emission. The full load fuel quantity is
also reduced when the permissible water temperature
is exceeded in the high speed range.
BMW DIESEL
11
DESCRIPTION AND OPERATION
Cruise control
The required driving statuses: acceleration or resume
driving speed can be set or selected using the
steering wheel switches. These functions are active
with a vehicle speed of more than 40 km/h (25 mph).
Air conditioning compressor cut-out
The ECM switches off the air conditioning compressor
during driving conditions demanding high torque
requirements (starting off, accelerating). The
compressor is also cut-out at high water temperatures
(more than 110
°
C) in order to protect the engine.
Self-diagnosis
The task of the self-diagnosis function is to detect
malfunctions in the DDE system and to make
available substitute values and emergency programs.
The ECM stores a record of faults, including
intermittent faults which can be interrogated using
TestBook.
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