Range Rover P38
17
EMISSION CONTROL
NEW RANGE ROVER
16
DESCRIPTION AND OPERATION
Evaporative emission control system - pre
advanced EVAPS.
The system is designed to prevent harmful fuel vapour
escaping to the atmosphere. The system comprises a
vapour separator (C) and a two way valve (D), both
located on the fuel filler neck (A), an Evaporative
Emissions (EVAP) canister and an EVAP canister
purge valve.
A
Fuel filler neck
B
External fill breather pipe
C
Fuel/vapour separator
D
Two way valve - fuel vapour to EVAP canister
E
Fuel vapour from fuel tank
During conditions of high ambient temperatures, fuel
in the tank vapourises, and pressure rises. Fuel
vapour enters the vapour separator and any liquid fuel
runs back to the tank. Three roll over valves (ROVs)
are fitted in the fuel tank vapour lines. These valves
prevent liquid fuel entering the vapour separator if the
vehicle rolls over. When pressure rises above 5 to 7
kPa (0.7 to 1.0 lbf/in
2
), the two way valve opens and
allows fuel vapour to flow to the EVAP canister where
it is stored in the canister’s activated charcoal
element. When the correct engine operating
conditions are met, the Engine Control Module (ECM)
opens the EVAP canister purge valve and vapour is
drawn from the canister, into the plenum chamber to
be burned in the engine. Fresh air is drawn into the
canister through a vent to take up the volume of
displaced vapour. If the two way valve should fail, or
the main vapour line becomes blocked, excess
pressure is vented to atmosphere through a valve in
the fuel filler cap. Similarly, the cap vent valve will
open to prevent the tank collapsing if excessive
vacuum is present.
When the temperature of fuel in the tank reduces,
pressure also reduces and vapour must be drawn
back into the tank. When tank pressure drops into
vacuum, the two way valve opens, allowing fuel
vapour to be drawn out of the EVAP canister into the
fuel tank. Again, fresh air is drawn into the canister to
take up the displaced volume.
