A faulty evaporative control system can cause fuel odours, fuel leakage, fuel tank collapse (vacuum build-up), excess pressure in the fuel tank, or a rough engine idle. These problems usually stem from a defective fuel tank pressure-vacuum cap, leaking charcoal canister valves, deteriorated hoses, or incorrect hose routing.

Evaporative control system maintenance and repair

Maintenance on an evaporative control system typically involves cleaning or replacing the filter in the charcoal canister. Look at Fig. 32-6. Service intervals for the canister filter vary. However, if the car is operated on dusty roads, clean or replace the filter more often.

Also inspect the condition of the fuel tank filler cap. Make sure the cap seals are in good condition.

Special testers are available for checking the opening of the pressure and vacuum valves in the cap. The cap should be tested when excessive pressure or vacuum problems are noticed.

All hoses in the evaporative system should also be inspected for signs of deterioration (hardening, softening, cracking). When replacing a hose, make sure you use special fuel resistant type hose. Vacuum hose can be quickly ruined by fuel vapours.

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