Volvo 780 Owner's Manual page 98

1987 Volvo 780
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.
Crankcase ventilation
The engine is provided 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 orifice nipple in the intake manifold should be cleaned every 60,000 miles (96,000 km).
It is recommended that the flame guard be cleaned every 20,000 miles (32,000 km).
pg. 99 Servicing
WARNING!
The ignition system operates at very high voltages. Special safety precautions must be followed to prevent injury. Always turn the
ignition off when:
Connecting engine test and diagnostic equipment to the vehicle (timing light, tach-dwell tester, ignition oscilloscope, etc).
Replacing ignition components e.g. plugs, coil, distributor, HT leads etc.
Do not touch any part of the ignition system while the engine is running. This may result in unintended movements and body injury.
Replacing spark plugs
The spark plugs should be changed every 25,000 miles (40,000 km). However, city driving or fast highway driving may necessitate
changing after 15,000 miles (24,000 km) of driving. When installing new plugs, be sure to fit the right type and use correct torque, see
"Specifications". When changing the plugs, check that the suppressor connectors are in good condition. Cracked or damaged connectors
should be replaced.
When changing spark plugs, clean the cables and cable terminals, also the rubber seals. If the car is driven on roads where salt is used during
the winter, coat the cables with silicone.
pg. 100 Automatic transmission
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