This system is intended to capture an accumulating fuel that comes from fuel tank, throttle body and intake manifold and which by right should not be released to the atmosphere as the fuel is composed of hydrocarbon. The early evaporative emission control systems entail a charcoal canister, linking lines, coolant temp sensor, a vacuum switch valve, the ECM, a check valve on the canister and some of the later models involved a
Vapor Pressure Sensor that is usually installed on the engine bay. The charcoal canister is installed under the vehicle near the fuel tank starting from the models of 2003 and 3.4 L V6; the vapor pressure sensor is used to detect leakage within the system. It accumulates fuel vapors in the canister if the engine is switched off and releases the same to be burnt in the engine if the engine is on. The canister contains of the check valve that has two balls, which depend on fuel tank pressure to regulate airflow. Problems like poor idle, stalling and driveability are some of the problems that can result from a bad check valve, a damaged canister or bad hoses. Crystal droplets or smell of fuel may call for checking the fuel lines or the canister for crack and kinking of hoses. In case fuel has spilled out from the canister it should be replaced and the related hoses examined for damages. Cracks on the canister surface can be observed, and a clogged filter or stuck check valve can be checked using low pressure air. The vacuum hoses should be identified and disconnected for canister replacement, then the mounting clamp bolts must be loosened and the hoses disconnected and the same procedure must be reversed for fixing.