Toyota 90910-12262 Valve, Duty Vacuum Switching

The fuel evaporative emission control (EVAP) system absorbs fuel vapors and releases them into the intake manifold during engine operation, where they mix with the incoming air/fuel mixture. When the engine is off, gasoline in the fuel tank and residual fuel in other components warm up and evaporate, producing unburned hydrocarbon fuel vapors that would waste gas and pollute the air if released. In an EVAP system, these vapors are routed through hoses to a charcoal canister, which stores them until the vehicle operates again, thanks to activated charcoal that absorbs many times its mass in hydrocarbon vapors. The system includes the charcoal canister, canister closed valve, EVAP system Vacuum Switching Valve, vapor pressure sensor, air filter, and refueling valve, with most components located near the canister beneath the vehicle. The vapor pressure sensor monitors the pressure inside the fuel tank and, when it detects excessive pressure, commands the canister closed valve to open, allowing vapors to migrate to the charcoal canister while also routing fresh air into the tank to prevent a vacuum. When the engine runs under the right conditions, the PCM commands the purge valve to open, allowing intake vacuum to pull vapors from the canister into the manifold for combustion. The refueling valve controls vapor flow during fuel tank filling, while the PCM regularly checks for leaks by inducing a vacuum in the system. For component replacement, the EVAP canister purge valve is accessed by removing the engine cover, disconnecting the electrical connector and hoses, and removing the mounting bolt. The EVAP canister requires raising the vehicle, disconnecting electrical connectors and hoses, and removing mounting bolts, while the Canister Closed Valve involves disconnecting a vacuum hose and removing mounting bolts. The EVAP canister air filter, located near the canister, is replaced by disconnecting hoses and removing the retaining bolt. The vapor pressure sensor, found on top of the fuel tank, requires removing the rear seat and carpeting, disconnecting the electrical connector, and removing the retaining ring before replacing the O-ring and installing a new sensor.

It is a known fact that in components such as the fuel tank and intake manifold, gasoline retained while the engine is off either in the fuel tank or stored in components of the infused fuel system like the intake manifold warms up and evaporizes creating unburned hydrocarbon fuel vapors that otherwise would waste gas and pollute the air if let out. The EVAP system uses three vacuum hoses to collectively pull vapors that are from the fuel tank, throttle body, and intake manifold and store them in the charcoal canister until the car is back in use again. This canister that is packed with activated charcoal, acts to sop these vapors. When the engine is running, it expels the vapors into the intake manifold combining them with the incoming combustible air-fuel ratio. It mainly consists of an air filter, a canister, a pump module, refueling valve, and purge valve and the most of them are placed under the car near the canister. The fuel vapor purge control valve controls the amount of fuel vapor from the fuel tank to the canister during purge and refueling modes and the fuel vapor check valve minimizes the amount of vacuum that draws fuel vapors into the canister. This again blows fresh air from the atmosphere through the air filter, into the canister to replace expelled vapour. In the pump module, the vapor pressure sensor checks on the pressure and throws the switch to PCM to turn on the purge valve whenever the pressure builds up. Under favorable circumstances, the PCM sends a signal to open the purge valve, and gets the burned vapors to be drawn by the engine while fresh air replaces the purged vapors. The PCM also carries out a leakage test on the system with the aid of the vacuum pump and the vapor pressure sensor and retaining a Diagnostic Trouble Code if any. For the component replacement, the EVAP canister purge valve is on the left side of the intake manifold next to the EVAP canister with hoses connected to it first needs to be disconnected then the valve can be removed. The EVAP canister air filter is placed close to the canister, and the fresh air hose is from the filter; the replacement involves the removal of the ABS harness bracket and disconnecting of the hoses. To replace the EVAP canister and refueling valve the car has to be lifted, the air filter has to be unscrewed and set aside, several electrical connectors and hoses had to be disconnected and the canister has to be unbolted in order to be removed. The pump module is reached by pulling the EVAP canister (Figure 5, 6 & 7), disconnecting hoses and unbolting the module from the canister and vice-versa for installation.