Fuel Injected Engines
When fuel tank pressure exceeds a preset value, 2-way valve opens and allows excess vapors to vent into canister. If excessive vacuum forms in fuel tank, 2-way valve opens to allow outside air into fuel tank through canister. Fuel filler cap acts as a safety valve if evaporation system fails.
When coolant temperature is above a preset value, purge cut-off solenoid valve on EFI Civic or thermo valve on all other models, along with the ECU, directs manifold vacuum to purge control valve to draw vapor into throttle body port. When coolant temperature is below this temperature, no vacuum is applied to purge control valve.