Chevrolet 17085891 Valve Asm,Evap Emission Pressure Control

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The evaporation control system is a basic and trouble-free part of the emissions network that reduces hydrocarbon emissions. It is a closed fuel system that redirects wasted fuel back to the gas tank and stores fuel vapors instead of releasing them into the atmosphere. The system requires little maintenance, but if there are issues, it should be inspected. To check the system, disconnect the fuel tank line at the charcoal canister, located behind the left headlight in the engine compartment. Check for liquid fuel in the line, which indicates a problem with the vent controls or gas cap. Apply 15 psi pressure to the fuel vapor line and look for excessive pressure loss. Check for fuel vapor smell in the engine compartment and around the gas tank. Remove the fuel filler cap and check for pressure in the gas tank. If there is a large pressure loss or fuel odor, inspect all lines for leaks or deterioration. To check the purge valve in the canister, start the engine, disconnect the vacuum signal line, and raise the engine speed to 1500 rpm to check for vacuum. If there is no vacuum, check the EGR operation. The purge line to the canister functions with the PCV vacuum source, so if there is no vacuum when the hose is disconnected, check the PCV valve vacuum. The charcoal canister and filter should be replaced at recommended intervals.

Inspecting and repairing or replacing hoses, canister, and components as necessary is recommended.