The EVAP system stops vapors from fuel system leakage from getting into the outdoors. Warm air causes fuel gas pressures to climb inside the tank until a critical point is reached. At this point, gases flow through the EVAP two-way valve to the EVAP canister, where they wait until we start the vehicle again. When it's the ideal moment, the PCM uses the canister purge valve to let fuel vapors go into the intake system, where they join with fresh air and burn in the engine cylinders in normal operation. Differing from model to model, the canister equipped with activated carbon goes under the vehicle on the right side of the fuel tank for 1995 BP DOHC models and all 1998-and-newer models, while some older models have the canister housed in the right rear corner of the engine space. The canister does not need regular maintenance and keeps the important parts close together: air filter, valve to close off vapor passage, solenoid valve switching fuel route, and fuel tank vapor pressure sensor. While in purging, the close valve above the fuel tank opens up to send fresh air from the filter into the canister. The fuel tank pressure sensor sits on top of the fuel pump and fuel gauge unit. It checks pressure inside the tank and sends information to the engine control computer to help monitor fuel systems. The PCM-controlled canister purge valve allows the engine to take in vapor from the canister and send it to the intake manifold through the engine compartment. When the fuel cleaner breaks, a clear fuel smell can appear because of three usual trouble spots: the fuel filler cap, hose connections, or the fuel canister. When you uninstall the gas cap, a sharp "whooshing" sound shows a too-high fuel pressure, meaning you need to look at the canister vapor lines and vent valve for any problems. Position-specific tools are needed for testing and diagnosis, something only profesionals can access. You can locate the EVAP canister purge valve when you pull up the engine hood, but you will need to look behind the fuel tank for the canister close valve if this is an older model car. With newer ones, the valve is on top of the canister itself. All you need to do is take out and put back in the fuel tank pressure sensor when needed. The EVAP canister installation happens once you lift the car to unhook its hoses and connections.