Volvo 819 E - Page 54

Group 28 Ignition systems
Design and function - System descriptions
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A
B
EZ-118K
' . 7 112
EZ-1 18K -Idling compensation
EZ-118K may be provided with one or two idling compensa t ion funct i ons ifthe car is equipped with automatic trans-
mission and/or air conditioning. If ei ther function is activated, [he control unit will advance the timing at id ling by eo
to compensate for the higher engine load.
A. Certain models equipped with automatic transmission are provided with a function which advances the timing
when a drive position is selected, to compensa te for th e increased load imposed by the torque converte r.
The s
tarting interlock switch (21) opens the relay coil (22) ground connec tion when the gear select or is moved to
position R. D, 2 or 1. This closes the relay contacts, supp ly ing 12 V to the timing advance terminal on the control
unit (1) . The con tr ol unit will advance the t iming if the idling (air con trol) switch (19) also indicates that the engine
is idling .
B.
Certain models equipped with air conditioning are provided with a function which advances the tim ing when the
AC compressor is switched in, thereby preven ting a fall in idling speed while maintaining the capacity of the AC
system .
The timing advance terminal on the control unit (1) is connected to the electromagnetic clutch circuit on the com-
pressor (23), and receives a 12 V supply when the pressure switch 124} closes to energize the clutch . The control unit
then advances the timing if the id l ing sw i tch (19) also indicates that the engine is idling .
On
the B 230 K eng i ne , the above compensat i on functions i ntervene on ly if the engine temperature exceeds 75"C on
1985-36 variants or 85"C on 1987 and later variants .
.. Idling compensation operated bv the ignition system control unit is not required on engines on which the idling valve is connect-
ed to the fuel system control unit (CIS system) or to a special CIScontrol unit. On engines of this type. the CIS valve ensures that
elClra air, 85 well as additional lue l, is supplied to the engine to compens ate for the inc reased load.
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