GMC 1997277 Valve,Evap Emission Canister Purge Solenoid

The Evaporative Emissions Control System (EVAP) work by confining fuel vapor inside the fuel system hence keeping it from escaping into the atmospher in a similar manner to the PCV system, but trapping the vapors inside the fuel tank until the pressure reaches a level that unseats the pressure relief valve wherein the vapors are redirected to a carbon canister for a brief time. When specific engine parameters are met vacuum from the manifold opens purge control valve to result into allowing the vapors to be drawn into the intake manifold for combustion. Three methods control this process: a ported vacuum source through the Thermo Vacuum Switch (TVS), manifold vacuum accompanied by an EVAP purge control valve, and an EVAP Purge Control Solenoid of the later models. The carbon canister is located at the different positions depending on the model year of your vehicle, if your vehicle model is before 2000 it is located in the engine compartment and if it is after 2000 it is placed underneath the car. Signs of EVAP system failures include fuel smell or a raw fuel leakage with prominence during hot weather. From 1996, models are equipped with a fuel tank pressure sensor that checks the leakage of vapor and sets a trouble code and the SERVICE ENGINE SOON lamp, typically due to a poorly tightened gas cap. The fuel filler cap is incorporated with a safety feature that is the two-way pressure-vacuum relief valve. To do this self-test the vacuum and vapor hoses should be checked for signs of wear and tear, the carbon canister should be examined and the gas cap seal should be examined. These tests include determining the presence of vacuum at three temperatures for the TVS and EVAP purge control solenoid. The vacuum-operated purge control valve should open very little when no vacuum is applied to it and quite a lot when vacuum is applied to it. Component replacement is performed at the TVS, solenoid, and carbon canister, and disconnecting/reconnecting with attention paid to the condition of seals; filters must be clean for particular components.

The role of the evaporative emissions control (EVAP) system is to manage fuel vapors by absorbing them from the fuel tank and then releasing into the engine's intake system where they will mix with incoming air/fuel mixture. The canister filled with activated charcoal for vapor absorption, purge valve, vent valve, fuel tank pressure sensor, fuel tank itself, and vapor and purge lines are some of the key components that make up this system though there might be slight variations in their components through different years and applications. The charcoal canister is a sealed carrier entered via a check valve by fuel tank vapor on its way through a second hose comprised of capillary slits which have been called vapor hose in order to let out or activate coal store the vapors. When certain conditions are met for instance; engine running or reaching preset temperature, the ECM/PCM opens both the purge valve as well as vent valve. Consequently, intake manifold vacuum drawn through a purge hose causes fumes from canister while normal engine operation consumes this fumes inside intake manifolds including combustion chambers. The EVAP purge solenoid is modulated by ECM/PCM to control the rate at which vapors flow from the canister to intake manifold. In cold conditions and during a hot start time delay, this solenoid remains de-energized according to ECM/PCEM. After warming up to operating temperature range specified for it, engine control module/ power control module (ECM/PCM) regulates purging of vapors into intake manifold based on engine running conditions. By varying energization time of solenoid OBD II models cycle purge valve control solenoid from 5 to 10 times per second for adjusting a flow rate. In such case PCM opens EVAP canister purge valve and closes vent valve during cold engine startup thereby creating vacuum throughout EVAP system after 1996 -2000 OBD-II models. PCM closes purge valve after reaching vacuum level, sealing the system and monitoring fuel tank pressure sensor voltage to set diagnostic code in case of leak detection. In these models, there is also a fuel tank pressure sensor that sends back a signal voltage to the PCM reflecting air pressure inside the fuel tank for detecting leaks. Of note, this system is protected by a five-year/ 50,000-mile warranty as mandated by federal law. In troubleshooting the system, start by checking hoses for damage, disconnection or misrouting. Repair any faulty hoses or replace them as required. For pre-EVAP controls model years check charcoal canister, purge control valve and vacuum hoses for possible problems. Late models contain electronic purge control so it is important to verify related fuses and wiring integrity pertaining to the purge and vent valves. These valves are typically closed with vapor flow starting following activation of PCM's solenoid. Although some limited testing may be performed, a scan tool must be used for thorough examination. If these initial checks do not identify the problem, consult a dealer service department or qualified repair shop. When replacing components, late model EVAP system hoses are equipped with quick-connect fittings requiring a twisting motion to loosen the seal before disconnection is made. The EVAP canister's location varies with the year and application while its removal involve disconnecting these hoses and removing bracket mounting bolt. During removal of early model vehicles, on top of electrical connector detachment one has to remove connecting lock tab on hose then take away mounting nuts/bolt from its intake manifold place or charcoal canister (Allen 83). On 1996-2000 models vent valve is mounted on bracket close to fuel tank which means raising of vehicle will have to occur since you should disconnect electrical connector from it then remove hose next release retainer in order displace vent valve from bracket (Allen 83). In 1996 through 2000 only, fuel tank pressure sensor is located on the fuel pump module hence removal of fuel tank follows disconnection of electrical connector and then releasing retaining clip to get rid of sensor from the pump (Allen 84). Put all replaced components back in place as we have done in reverse order.

The EVAP system is designed to prevent fuel system vapors, containing unburned hydrocarbons, from escaping into the atmosphere.

In cold conditions and during a hot start time delay, the ECM/PCM keeps the solenoid de-energized. Once the engine reaches the correct operating temperature, the ECM/PCM regulates vapor purging into the intake manifold based on the engine's running conditions. It does so by cycling the purge valve control solenoid ON and OFF approximately 5 to 10 times per second, adjusting the flow rate.

To remove the EVAP canister vent solenoid, start by disconnecting the electrical connector and quick-connect fittings from the solenoid. Then, remove it from its mounting bracket.

To remove the EVAP canister vent solenoid, start by disconnecting the electrical connector and quick-connect fittings from the solenoid. Then, remove it from its mounting bracket.