Description
The Evaporative Emission Control System prevents fuel vapor stored in fuel tank from vaporizing into the atmosphere. When the fuel evaporates in the fuel tank, the vapor passes through vent hoses or tubes to a canister filled with charcoal. The canister temporarily holds the vapor in the charcoal. The ECM will control the system in order to draw the gathered vapor into the combustion chambers during certain operating conditions. Engine manifold vacuum is used to draw the vapor into intake manifold.
Scheme 443
A ratchet tightening device on the threaded fuel filler cap reduces the chances of incorrect installation, which seals the fuel filler. After the gasket on the fuel filler cap and the filler neck flange contact each other, the ratchet produces a loud clicking noise indicating the seal has been set.
Scheme 444
Scheme 445
Scheme 446
Scheme 447
- Turn the ignition switch OFF and disconnect the battery negative (-) cable.
- Lift the vehicle.
- Disconnect the canister close valve connector (A).
- Disconnect the ventilation hose (B) from the fuel tank air filter and canister close valve.
- Remove the fuel tank air filter assembly after removing bolts (C). (Scheme 445): Identifying Mounting Bolts (C) on Fuel Tank Air Filter
- Release the lever (A), and then separate the canister close valve (B) from the fuel tank air filter (C) after rotating it in the direction of the arrow in the illustrations below. (Scheme 446): Removing Canister Close Valve (Scheme 447): Separating Canister Close Valve From Fuel Tank Air Filter
NVLD(Natural Vacuum Leakage Detection) module is located between the canister and the fuel tank air filter.
NVLD module is an integral part of the monitoring system. The NVLD module has a pressure switch and a temperature sensor. The temperature and pressure switch are checked every 10 minutes during engine off.
While the vehicle is turned off, the temperature and pressure switch monitored. As the fuel system cools down, the pressure should drop. The Evap system checks for small leaks by checking the pressure switch state as the temperature changes. If the pressure does not drop enough as the temperature drops, a leak is detected.
It closes off the air inlet to the canister for the Evaporative Emissions System and also prevents fuel vapors from escaping from the Canister when the vehicle is not operating.
When the switch is closed due to pressure decrease, a timer is started and switch closed duration is monitored This information will be provided to the ECM for very small leak error detection. Large leak/fuel cap off detection is performed during engine running.
