DESCRIPTION
The sealed fuel evaporation system prevents gasoline vapors from escaping to the atmosphere. The system consists of a non-vented fuel tank filler cap, an expansion chamber built into fuel tank, an activated charcoal canister, safety valves, and a series of connecting lines which interconnect the components between fuel tank and air cleaner.
OPERATION
Expanded fuel caused by high temperatures is collected in expansion chamber of fuel tank. Fuel is returned to main tank by venting action as fuel is used from main tank. When engine is stopped, fuel tank vapors flow through a vent line to charcoal canister, where they are stored.
When engine is running above idle speed, intake vacuum draws fresh air through charcoal canister and pulls stored vapors into the intake system through the air cleaner.
When engine is at idle, fuel vapors flow from the charcoal canister to the intake manifold to be burned. A safety valve, located between charcoal canister and fuel tank, closes to prevent fuel leakage if vehicle turns over.
The charcoal filter valve, located between the charcoal canister and air intake duct, reduces hydrocarbon emissions by closing at idle to prevent vaporized fuel from entering air intake.
As speed increases, the charcoal filter valve opens and allows vapors, stored in the charcoal canister, to enter intake duct to be burn by the engine.
4000S & 4000S Quattro
With ignition off, remove hose connector from top of charcoal filter valve and blow into valve port. Air should not flow through valve. If air flows through valve, replace valve.
5000S & GT Coupe
Remove valve and attach a hand vacuum pump to the small connection. Blow into the large opening. Air passage must be blocked, if not replace. Apply vacuum to valve with pump and blow into large opening. If air passage is not open, replace valve.
MAINTENANCE
Every 15,000 miles check all components for leakage, damage or deterioration. Replace as required.