GM 25903990 Canister Assembly, Evap Emission

You can Select Your Vehicle to check if 25903990 fits your vehicle.

The Evaporative Emissions Control (EVAP) system is a system designed to prevent the escape of fuel system vapors containing unburned hydrocarbons into the atmosphere. On hot days, fuel vapors that are trapped in the fuel tank continue to expand until they reach a certain pressure limit. The liquid fuels expelled from this tank move through the evaporative valve and canister, where they temporarily collect before being burnt up in an operating engine. There are times when the Powertrain Control Module (PCM) opens up the canister purge solenoid when suitable conditions are met like; warmed up engine, vehicle is at speed or there's a moderate to heavy load on the engine. This allows fuel vapour in the canister to be drawn into the intake manifold chamber for mixing with air/fuel mixture before it gets used in the combustion chambers. Both component and layout of EVAP system are critical including EVAP canister located above fuel tank consisting of activated carbon to hold vapours, fuel tank pressure sensor atop of fuel pump/fuel level sensor module and EVAP canister vent solenoid behind left rear wheel well fender liner which normally is opened but seals off for inspection/maintenance on EVAP system. It should be noted that with its duty cycle dependent on factors like vacuum in intake manifolds and data from sensors, vapor flow from canister to intake manifold is regulated by EVAP canister purge solenoid under PCM control. With all these advantages it must be remembered that troubleshooting an EVAP system requires specialized tools and training because these problems cannot be detected by ordinary people using normal senses, although some symptoms may be indicative of related problems. These include smelling gasoline on warm days primarily caused by loose or broken EVAP hose connections among other things. One method consists of removing the gas cap and listening for pressure release as signs of too much vaporized petrol within tanks, while professionals need full diagnostic test. The replacement of the EVAP canister purge solenoid on V6 engines requires removal of electrical connections, lines, and a mounting bolt for installation or reinstallation procedures since it is lodged at the left front part of the intake manifold. On the other hand, in case of V8 engines, you have to remove an engine cover to access the EVAP canister purge valve that is located at the top of rear intake manifold portion prior to disconnecting electrical connector and lines for removal and installation purposes. The EVAP canister vent solenoid located behind the left rear wheel well can be accessed by jacking up and securing the vehicle; disconnecting all electrical connectors, hoses then slide solenoid upward to remove or reinstall it. Finally, raising the vehicle disconnecting labeled hoses with electrical connectors then detaching it from its mounting bracket completes EVAP canister situated on top fuel tank's installation process. Above all, fuel tank pressure sensor atop fuel pump/fuel level sensor module mounting flange needs a raised motorcar body coupled with removal of fuel tank before eventually dismantling and reinstalling sensor by means of undoing electric plug.

Fuel vapors trapped in the fuel tank expand on warm days until they reach a specific pressure threshold. At this point, the fuel vapors are directed from the fuel tank through various components to the EVAP canister, where they are temporarily stored until they can be consumed by the engine during normal operation.