Volvo 240 1989 Service Manual page 12

Design and function
Fuel system LH2.4 - 240
Th e start-up program provides for two injection
durations per revolution.
The cold-start valve is activated when the tem ­
perature is at -15°C (5°F) or below, and the engine
speed is under approximately 900 rpm. Once the
rpm exceed the pre-programmed limit, the cold­
start valve Is turned off.
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During normal driving conditions, injection dura ­
tion is regulated mostl y with referen ce to signals
trom the air mass meter.
The choke provides a richer fuel mi xture to the
engine up to an engine tempe rature of 60°C
(140"F).
Injection duration increases during acceleration.
Knock enrichment provides a richer fuel mixture
to cou nteract kn ock when the fuel system's anti­
knock control system has been unsuccessful at
reducing knock by adjusting downward severat
degrees on all cylinders. Knock cause high
combustion temperatures. When knock occurs,
the control unit increases the amount of fuel in
order bring the combus tion temperature down
and reduce the knock.
Excess rpm is prevented via a rotation speed
limiter which turns 011 the injectors. They are
turned on again when the engine rotation is re ­
du ced.
At full load, a richer airlluel mixture is used to
provide maximum engi ne power and to lessen the
el1ects of combustion heat on the engine and the
catalytic converter.
During deceleration, fuel injection is discontin­
ued above 1,800 rpm in all gears. It is resumed at
1,400 to 2,000 rpm, depending on engine tem­
perature.
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