Enhanced Evaporative Emission (EVAP) Natural Vacuum Leak Detection (NVLD) System - Fiesta
The enhanced EVAP NVLD system consists of the capless fuel tank filler pipe, EVAP canister, normally closed EVAP canister purge valve, fuel tank, fuel tank mounted vapor control valve, fuel vapor hoses, fuel vapor vent valve, intake manifold hose assembly, the NVLD module, and powertrain control module (PCM). The PCM and the NVLD module check the entire EVAP system, including all the fuel vapor hoses from the NVLD module to the intake manifold, for a leak when the calibrated conditions are met. For additional information on the EVAP system components, refer to ENGINE CONTROL COMPONENTS .
- The PCM uses inputs from the engine coolant temperature (ECT) sensor, the fuel level input (FLI), the intake air temperature (IAT) sensor, the mass airflow (MAF) sensor, the NVLD ambient air temperature sensor, the vehicle speed sensor (VSS) and the NVLD module to determine conditions of the enhanced EVAP system. The PCM uses the combination of these signals to determine when to activate the EVAP leak check monitors.
- The PCM uses inputs from the fuel level input (FLI), the NVLD ambient air temperature sensor, and the EVAP canister load to determine the desired amount of purge vapor flow to the intake manifold for a given engine condition. The PCM then outputs the required signal to the EVAP canister purge valve. The PCM uses the enhanced EVAP system inputs to evacuate the system using the EVAP canister purge valve.
- The PCM outputs a duty cycle between 0% and 100% to control the EVAP canister purge valve.
- The NVLD module vacuum switch and the NVLD relief valves seal the enhanced EVAP system from the atmosphere during the EVAP leak check monitors.
- A valve inside the fuel vapor tube assembly prevents liquid fuel from entering the EVAP canister and the EVAP canister purge valve under any vehicle altitude, handling, or rollover condition.