In order to determine when the fuel valve shall open or
close, the
control unit has access to signals from sen-
sors and switch contacts.
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 closed (when the
fuel valve is closed fuel is sprayed into the cylinder).
The parameters which govern the amount of fuel
injected 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
engines that operate at high altitude. This function lim-
its 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 pro-
tect 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
language on the instrument panel, depending on the
equipment used. If a fault code is obtained as a flash-
ing 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 work-
shops.
In case of serious disturbances, the engine is shut
down completely or the control unit decreases the
power output (depending on the application). Once
again, a fault code is set for guidance in any fault trac-
ing.
30-0 General
32 47701632 10-2013 © AB VOLVO PENTA