1 / 16

Evaporative Emissions Control Systems (EVAP)

Evaporative Emissions Control Systems (EVAP). Purpose Enhanced and Non-Enhanced Components Function Finding Faults. Purpose:. To trap and hold gasoline vapors (HC) To deliver vapors to engine airflow for complete burning Provides system ventilation to allow purging

roykeene
Download Presentation

Evaporative Emissions Control Systems (EVAP)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Evaporative Emissions Control Systems (EVAP) Purpose Enhanced and Non-Enhanced Components Function Finding Faults

  2. Purpose: • To trap and hold gasoline vapors (HC) • To deliver vapors to engine airflow for complete burning • Provides system ventilation to allow purging • Provides pressure relief to prevent excess pressure inside fuel tank

  3. 2 Types of Systems • Non-Enhanced • Diagnostic ability is limited to purge detection and monitoring • Enhanced • Monitors purge flow • Monitors system integrity • Leak checking • 1996-2000: leak checking to .040 in. • 2000-up: leak checking to .020 in.

  4. Components: • Carbon canister • Traps and holds fuel vapors for burning by engine • Purge valve/ Purge solenoid • Controlled by PCM to allow canister purging during certain conditions • Vacuum lines • Connect tank to canister • Connect canister to engine • Fuel tank filler cap • Seals fuel tank • Allows for pressure relief • Prevents excessive vacuum from collapsing tank • Fuel expansion tank • Prevents liquid fuel from entering canister • Fuel Tank Pressure Sensor (Enhanced) • Vent valve (Enhanced) • Provides fresh air for system purging • Can be used to seal system to check for leaks

  5. Function: • As fuel heats up: vapors form and are vented to canister • Canister is filled with activated charcoal • Fuel vapors attach to carbon surface • 1 gram of charcoal contains surface area equal to ¼ acre • Holds 1/3 of its own weight in fuel vapors • As system is purged, vapor molecules are pulled from carbon surface

  6. Function: • Pressure build-up is caused by: • Volatility rates • Fuel tank size • Fuel level inside tank • Fuel slosh • Temperature • Fuel return

  7. Function: • Purging is closely controlled • Excess fuel vapors can upset air/fuel ratio • Purging is allowed: • Closed loop • Cruising speeds • Purging is not allowed: • Open loop • Idle or deceleration • WOT

  8. Finding Faults • Two types of complaints: • Fuel vapor smell • MIL illumination • Retrieve DTC’s • Check freeze frame data for ECT and VSS • Check TSB‘s, recalls and PCM reflashes • DTC’s: • Purge control circuit failures • Purge flow failures • Leak detection DTC’s

  9. Finding Faults • Follow manufacturer’s diagnostic troubleshooting procedure • Purge control circuit failures: can be checked with bidirectional scan tool • Command purge valve on and listen for clicking sound • With valve commanded on check for air flow through valve • Check power and ground wires with voltmeter • Purge valve can be manually activated with jumper wires

  10. Finding Faults • Purge flow failures: can be caused by leakage or restriction preventing purge • Smoke machine: insert probe into test port and watch machine’s flow meter • Proper flow eliminates possibility of restriction in system • Improper flow indicates system is restricted: isolate system and continue checking

  11. Finding Faults • Leak checks: connect smoke machine and close vent solenoid • Vent solenoid can be closed with scan tool, manually cycled with jumper wires or vent pinched with suitable tool • Smoke machine should indicate no flow if system is free from leaks • If leaks are present, smoke will be visible

  12. Locating Leaks • Smoke testing: uses low pressure smoke introduced to system from test port • Allows for visual leak detection • Nitrogen gas pressurization • Very low pressure (> 1 psi) • Uses sound amplification for detecting leaks

  13. Toyota Evaporative Emissions

More Related