Description And Operation: Notes
DESCRIPTION
The Evaporative Emissions system consists of the following components:
| EVAP SYSTEM COMPONENTS | |||
|---|---|---|---|
| CALLOUT | DESCRIPTION | CALLOUT | DESCRIPTION |
| 1 | Refer to CANISTER FRESH AIR FILTER . | 11 | Recirculation Tube (metal portion) (FTPS to Fuel Filler Tube) |
| 2 | Filter Hose (Filter to ESIM) | 12 | Gas Cap or Cap-less Refueling Unit (if equipped) |
| 3 | Refer to EMISSION SYSTEM INTEGRITY MONITOR (ESIM) . | 13 | Fuel Filler Tube |
| 4 | Refer to CHARCOAL CANISTER . | 14 | Multi-Function Control Valve (MFCV) in the Fuel Delivery Flange Refer to INTERNAL TANK VENT VALVES . |
| 5 | Canister Tube (Fuel Tank to Canister) | 15 | Grade Vent Valve (GVV) Tube (GVV to MFCV) |
| 6 | Purge Tube (Purge Solenoid to Canister) Refer to EXPANSION CHAMBER . |
16 | Grade Vent Valve (GVV) Refer to INTERNAL TANK VENT VALVES . |
| 7 | Refer to EVAPORATIVE EMISSIONS PURGE SOLENOID . | 17 | Fuel Tank |
| 8 | Manifold Hose (Purge Solenoid to Engine Manifold) | 18 | Inlet Check Valve (ICV) |
| 9 | Recirculation Tube (Fuel Tank to FTPS) | 19 | Hose - Fuel Filler Tube to ICV |
| 10 | Refer to FUEL TANK PRESSURE (FTP) SENSOR . | - | - |
OPERATION
EVAP SYSTEM OPERATION: The Evaporative Emissions System is designed to manage fuel vapors. The Powertrain Control Module (PCM) monitors the performance of the Evaporative Emission System. The system uses the principle of Natural Vacuum Leak Detection (NVLD) to determine the integrity of the system. When fuel vapors build and exit the Fuel Tank they are routed and stored in the Charcoal Canister. Fuel vapors entering the Charcoal Canister are absorbed by the charcoal filter until they can be drawn into the Intake Manifold during purging and burned by the engine.
The two main areas being monitored are the integrity of the system against leaks and the ability of the system to purge fuel vapor from the canister to the Intake Manifold.
- The basic strategy used for leak testing is that in a sealed system , pressure will naturally increase or decrease in relation to temperature. The Evaporative System Integrity Monitor (ESIM) Switch is used for all leak fault detection. There is a vacuum actuated switch that closes when the vacuum reaches a calibrated threshold. If the switch closes it indicates that the system is not leaking.
- The basic strategy used for purge performance testing is that as flow through the system increases, so does the pressure drop in the system. The Fuel Tank Pressure (FTP) Sensor is used for purge fault detection. The PCM monitors the Fuel Tank Pressure Sensor and looks for increasing vacuum in the Fuel Tank with increasing purge flow. Conversely, it looks for decreasing vacuum in the Fuel Tank with decreasing purge flow.