Purge Valve

WARNING: This page is about a different car, the 2018 Jaguar XF. However, it is still accessible from the selected car via links, so may be relevant.

The Powertrain Control Module (PCM) waits until the engine coolant temperature is running above 40 °C (104 °F), with closed loop fuel operational, before the purging process is activated. Under these conditions the engine should be running smoothly with no warm up enrichment. The purge valve duty (and flow) is initially ramped slowly because the vapor concentration is unknown and a sudden increase in purge could cause the engine to stall or loss of air fuel ratio control to occur. The concentration is then determined from the amount of adjustment that the closed loop fueling is required to make to achieve the target air fuel ratio. Once the concentration has been determined, the purge flow can be increased and the injected fuel can be pro-actively adjusted to compensate for the known purge vapor and the target air fuel ratio control is maintained.

When the purging process is active, fresh air is drawn into the evaporative emissions canister via the canister vent port.

On NAS market vehicles the fresh air is drawn into the evaporative emissions canister via the Diagnostic Module Tank Leakage (DMTL) filter and pump.