L322 Range Rover System Description and Operation
ENGINE MANAGEMENT SYSTEM – V8
DESCRIPTION AND OPERATION 18-2-55
Emissions
Evaporative Emissions (EVAP) Purge Valve
The EVAP purge valve is located on the LH side of the engine in the line between the charcoal canister and the inlet
manifold. The EVAP purge valve is part of the EVAP control system and is used to control the extraction of fuel vapour
stored in the EVAP canister.
The EVAP control system reduces the level of hydrocarbons released into the atmosphere by fuel vapour venting from
the fuel tank. The system comprises fuel cut off valves, a vapour separator, a two way valve, vent lines, the canister
and the purge valve.
Purge Valve
The ECM controls the amount of vapour drawn from the charcoal canister by controlling the length of time the purge
valve is open. It controls the length of time it is open by supplying the purge valve with a PWM voltage. Control is used
to maintain the required level of emissions, as a hydrocarbon vapour level of 1% can affect the air/fuel ratio by as
much as 20%.
The ECM can diagnose faults with the purge valve and will store the related fault codes, along with details of the
engine speed, battery voltage and intake air temperature. The driver may notice the following effects if the purge valve
fails in the open position:
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The engine may stall periodically when returning to idle
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The engine may suffer from poor idle quality
