Catalytic Converter; Distribution Pipe; Fuel Pressure Regulator - Volvo 240 1989 Service Manual

Design and function
The catatytic converter cleans the exhaust gases in
three ways :
1 - by incinerating unburned hydrocarbons (HC) at
high temperature, releasing the residue as
steam (H,O).
2 - by converting carbon oxide (CO) to carbon diox ­
ide (CO,) through oxidation.
3 - by reducing nitrogen oxides (NO,) to gaseous
nitrogen (N).
90 to 95% of the dangerous gases are rendered
hamnless.
o
Di stribution pipe
Theincoming fuel feed line, pressure regulator, injec ­
tors and cold start valve are connected to the distri­
bution pipe.
Fuel sys tem LH2.4 - 240
Catalytic converter
In order to be able to operate as inte nd ed, th e
catalytic converter is dependent on correct informa ­
tion from the Lambda-sand. The air/fu el mixture must
be adjusted so that fuel is completely burned in the
engine prior to the exhaust gases reaching the cata ­
lytic converter.
The converter can be damaged through overh eating
if unburnt fuel is emitted in the exhaust where oxygen
is present.
This can happen if a large amount of unburnt fuel
reaches the catalytic converter prior to starting . It can
also happen if there is a loose ignition cable, and a
cylinder pumps unburned fuel into the exhaust.
Lead in the fuel will quickly aHect the Lambda-sond
and cause the exhaust gas cleaning function to stop
working. If tllis happens , the Lambda-sond will stop
providing the information needed
by the
con trol unit
to set the fuel mixture and the
cataly~c
oonverterw ill
then be destroyed.
The active area is about 20,000 sq. m (2 15.000 sq.
ft .) .
(California EGR converter approx, 32.000 sq. m
~ 345,000
sq,
fl.) The precious metal content is about
2 grams (.07 oz) of platinumlrhodlum,
®
Fuel pressure regulator
The fuel pressure regulator ensures that the fuel
pressure remain s constant at the Injectors . Using a
vacuum tube connected to the eng ine Intake man i­
fold, the fuel pressure is kept at 300kPa (42 psi)
above (below) the intake manifold pressure . In this
way
the pressure over the injectors is kepi constant,
regardless of throttle pOSition . The amount of fuel
injected depends entirely on the Injection duration.
Excess fuel is returned to the fuel lank via a return
pipe.
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