Volvo 780 Owner's Manual page 101

1989 Volvo 780
pg. 99 Servicing
Catalytic converter
This is a supplementary device in the exhaust system, designed to clean exhaust gases. This device is mainly a container with a ceramic
material insert, designed to let the exhaust gases pass through channels in the insert. The channel walls are covered by a thin layer of
platininum-palladium. These metals act as catalysts, permitting a chemical reaction to occur without actually taking part in it.
The emission(CO, HC, NOX) content will increase if the catalytic converter is damaged. Lambda-sond equipped vehicles use Catalytic
Converters containing platinum and rhodium.
Torque Catalytic Converter mounting bolts
The Catalytic Converter mounting bolts should he torqued at the 600 - 1,200 mile (1,000 - 2,000 km) service.
Caution:
Vehicles with Catalytic Converter must use unleaded fuel only. Otherwise the Catalytic Converter will become ineffective See "Fuel
requirements".
Lambda-sond (oxygen sensor) System
This is an emission control system designed to Reduce emissions and improve fuel economy. An oxygen sensor monitors the composition
of the exhaust gases leaving the engine. The exhaust gas analysis is fed into an electronic unit which continually influences the injectors.
This adjusts the air-fuel ratio to provide optimum conditions for combustion and efficient reduction of the three major pollutants
(hydrocarbons, carbon monoxide and nitrous gases) by a 3-way catalytic converter.
pg. 100 Servicing
Evaporative control system
The 780 is equipped with a gas evaporative control system, which prevents gasoline fumes from being released into the atmosphere. The
system is comprised of an expansion chamber in the fuel tank, a roll-over valve on the cross member in front of the fuel tank, and a charcoal
canister with built-in vacuum valve under the hood.
The components are interconnected by hoses which channel fuel vapor from the gas tank to the charcoal filler, where it is stored until the
engine is started and then drawn into the engine's fuel induction system.
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