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Volvo 1990 740 Model
The 740 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, and a
charcoal canister with built-in vacuum valve under the left-front wheel housing.
The components are interconnected by hoses which channel fuel vapor from the gas tank to the charcoal
filter, where it is stored until the engine is started and then drawn into the engine's fuel-induction system.
Crankcase ventilation
The engine is equipped with positive crankcase ventilation which prevents crankcase gases from being
released into the atmosphere. Instead, the crankcase gases are admitted to the intake manifold and
cylinders.
PCV system
The PCV nipple in the intake manifold should be removed and inspected every 60,000 miles (96,000
km).
Check/replace hoses at the same time.
Exhaust Gas Recirculation (EGR)
This system operates by returning some of the exhaust gases to the engine to be recombusted: since this
lowers the combustion temperature the amount of nitrogen oxides released into the atmosphere is
reduced.
file:///K|/ownersdocs/1990/1990_740/90740_22.htm (6 of 7)12/30/2006 8:26:07 AM
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