EVAP Canister Purge Valve

WARNING: This page does not describe the selected car, but rather 15 other vehicles, including the 2015 Jaguar XFR-S, 2015 Jaguar XFR, 2015 Jaguar XF, 2014 Jaguar XFR-S, and 2014 Jaguar XFR. However, it is still accessible from the selected car via links, so may be relevant.

The ECM waits until the engine is running above 55 °C (131 °F) coolant temperature 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 EVAP canister purge valve duty (and flow) is initially ramped slowly because the vapor concentration is unknown (a sudden increase in purge could cause unstable engine running or cause it to stall due to an extremely "rich" air/fuel mixture). The concentration is then determined from the amount of adjustment that the closed loop fueling is required to make to achieve the target AFR (air fuel ratio). Once the concentration has been determined, the purge flow can be increased rapidly and the injected fuel can be pro-actively adjusted to compensate for the known purge vapor and the target AIR control is maintained.

When the purging process is active, fresh air is drawn into the EVAP canister via the DMTL filter and pump on NAS vehicles, or via the vent port on the EVAP canister of non NAS vehicles.

The EVAP canister purge valve is located on the LH (left-hand) side of the engine, below the ignition coils cover. A vapor pipe is routed from the EVAP canister purge valve to the inlet of the intake manifold (naturally aspirated vehicles) or the supercharger (supercharged vehicles). The EVAP canister purge valve is controlled by the ECM and is operated when engine operating conditions are correct to allow purging of the EVAP canister. The EVAP canister purge valve is a solenoid operated valve which is closed when de-energized.

A vapor pipe, which runs parallel with the fuel delivery line under the LH side of the vehicle, connects the EVAP canister purge valve to the EVAP canister.

The EVAP canister purge valve is operated at 10 Hz by a PWM (pulse width modulation) signal from the ECM. At this high frequency, the pulses of fuel vapor flow into the intake manifold/supercharger in an almost continuous flow. The valve operates between 7% and 100% duty or mark space ratio (percentage open time).

Atmospheric pressure is higher than the pressure at the inlet of the intake manifold/supercharger under all throttle settings and engine running conditions. It is this pressure differential that causes air to flow through the EVAP system to the engine.