Evaporative emission control system
Description and Operation
Description
The system prevents fuel vapors from escaping from the fuel tank into the atmosphere. When fuel in the fuel tank evaporates, the vapor flows through the vent hoses or tubes into the charcoal canister filled with activated charcoal, which temporarily holds the vapor.
When the ECM determines that vapor accumulation has occurred under specific conditions, it uses the intake manifold vacuum to draw the vapor into the combustion chambers.
Schematic diagrams
CIRCUIT DIAGRAM
| 1. Air cleaner 2. Fuel supply line and injector 3. Engine 4. Purge control solenoid valve (PCSV) 5. Low-pressure pump |
6. High-pressure fuel pump 7. Filler neck 8. Fuel tank cap 9. Fuel tank |
Charcoal canister
The canister is filled with activated charcoal and absorbs fuel vapors from the fuel tank. The fuel vapors accumulated in the canister are drawn into the intake manifold by the ECM/PCM when appropriate conditions are met.
PURGE CONTROL SOLENOID VALVE (PCSV)
The purge control solenoid valve (PCSV) is installed in the line connecting the charcoal canister and the intake manifold. The solenoid valve is a functional control valve and is controlled by a signal from the ECM/PCM.
To draw the absorbed vapor into the intake manifold, the ECM/PCM opens the PCSV; otherwise, the passage remains closed.
Fuel filler cap
The ratchet mechanism on the fuel tank cap prevents the cap from being overtightened, thereby ensuring the filler neck is fully sealed. When the cap seal contacts the filler neck while tightening, the mechanism produces an audible click, indicating the fuel cap is correctly installed.
Test yourself
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