Volvo TAD650VE, Руководство по ремонту

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EMS 2 - “Engine Management System” Group 30: Electrical system
10
Fuel control
The amount of fuel injected into the engine and the in-
jection advance are fully electronically controlled, via
fuel valves in the injectors, once the control unit has
analyzed the engine’s fuel requirements.
This means that the engine always receives the cor-
rect volume of fuel in all operating conditions, which
offers lower fuel consumption, minimal exhaust emis-
sions etc.
The control unit monitors and reads the injectors to
ensure that the correct volume of fuel is injected into
each cylinder, and it calculates and set the injection
advance. Control is mainly done with the help of the
speed sensors, fuel pressure sensor and the com-
bined sensor for boost pressure/boost temperature.
The control unit controls the injectors via a signal to
the electromagnetically operated fuel valve in each in-
jector, which can be opened and closed.
Calculation of fuel quantity
The quantity of fuel to be injected into the cylinder is
calculated by the control unit. The calculation deter-
mines the time that the fuel valve is open (when the
fuel valve is open fuel is sprayed into the cylinder).
The parameters which govern the amount of fuel in-
jected are:
• Demanded engine speed
• Engine protector functions
• Temperature
• Boost pressure
Altitude correction
The control unit contains an atmospheric pressure
sensor and an altitude compensation function for en-
gines that operate at high altitude. This function limits
the fuel volume in relation to ambient air pressure.
This is to prevent smoke, high exhaust temperature
and to protect the turbocharger from overspeeding.
Diagnostic function
The task of the diagnostic function is to discover and
localize any malfunctions in the EMS 2 system, to
protect the engine and to inform about any problems
that occur.
If a malfunction is discovered, this is announced by
warning lamps, a flashing diagnostic lamp or in plain lan-
guage on the instrument panel, depending on the equip-
ment used. If a fault code is obtained as a flashing code
or in plain language, this is used for guidance in any fault
tracing. Fault codes can also be read by Volvo’s VODIA
tool at authorized Volvo Penta workshops.
In case of serious disturbances, the engine is shut
down completely or the control module decreases the
power output (depending on the application). Once
again, a fault code is set for guidance in any fault
tracing.