Test Group TBM2.8VJGKEK
Evaporative System Monitoring General Description - The evaporative system monitoring permits the detection of leaks in the evaporative emission control system with a diameter of 1 mm and up. See Fig 1.
The evaporative emission control system is hermetically sealed off from the atmosphere by means of a shut-off valve at the charcoal canister. When the purge valve opens, the engine generates a vacuum in the tank. After closing the purge valve, pressure increase is measured by a tank pressure sensor. If vacuum increases above a defined threshold a leak is detected. As part of the vacuum check, purge flow is verified. For vapor generation test and EVAP system diagnosis, see Fig 2-Fig 5 .
Monitoring Structure - To start diagnosis function several conditions have to be satisfied:
- No malfunction related to vehicle speed, coolant and intake air temperature, idle speed, oxygen sensor, purge valve, tank pressure sensor, shut-off valve or throttle position.
- Coolant temperature greater than 176°F (80°C).
- Altitude less than 8202 feet.
- Canister purge time greater than 360 seconds after start.
- Canister purge time between 10-150 seconds depending on canister saturation.
- Vehicle speed = 0.
- Engine at idle.
- Tank pressure within -.05 to .05 psi.
- Pressure increase due to vapor generation is less than threshold.