Lotus Evora Service Notes page 218

Lotus Service Notes
LN.1 - GENERAL DESCRIPTION
The 60 litre fabricated stainless steel fuel tank is mounted within an open bottomed chassis crossmember
ahead of the engine bay and beneath the floor of the cabin rear compartment. The fuel filler neck is connected to
the RH rear corner of the tank, with a breather connection at the LH front corner, and the pump/gauge sender unit
mounted centrally in the front upper surface, accessible via removeable panels in the body floor and chassis.
In order to meet stringent vapour emissions legislation, various components are housed within the tank,
and include the pump assembly and filter, a fill level vent valve, and two gradient vent valves. The pump as-
sembly supplies fuel to the engine fuel rail at a controlled pressure using a non-circulation system.
Inside the tank, a spring loaded flap at the bottom of the filler pipe, allows fuel to enter the tank but inhibits
fuel surge up the pipe during cornering forces or extreme vehicle attitude changes. During the filling process,
tank ventilation is provided by a fill level vent valve (FLVV) mounted within the tank to the left of the pump.
The FLVV allows venting of fuel vapour to the charcoal canister via pipework connecting to the tank breather
spigot at the left hand front top corner of the tank. When the fuel level reaches the design maximum, a float ball
valve shuts off the vent, causing a pressure rise in the filler neck and triggering the nozzle auto-shut off. The
float valve will function in a similar manner to reduce fuel spillage in the event of a vehicle roll-over. In order
to ensure tank breathing when the car is parked on a side slope with a near-full tank, at which time the FLVV
may be closed, a gradient vent valve is fitted at each end of the tank and connected to the same tank outlet
spigot. These valves allow a slower rate of vapour escape and also include a low pressure holding valve and
roll-over shut-off functionality. Note that with the exception of the fuel pump/sender unit, none of these 'in-tank'
components are serviceable other than by fuel tank replacement.
The tank structure incorporates a system of baffles surrounding the pump assembly to ensure that the
pump inlet is kept submerged during extreme dynamic forces until the fuel level becomes near empty. The
modular fuel pump/gauge sender assembly is mounted inside the tank, clamped to the top surface by eight
studs. The pump uses an electric motor to power an integrated turbine, to draw fuel through an intake strainer
sock, and pump the fuel through the motor body and a non-return valve, to exit into a filter chamber incorpo-
rated into the housing of the pump/sender unit. After the filter, a pressure regulating valve controls the output
line pressure to around 3.2 bar, spilling excess fuel back into the tank, and supplying the pressurised fuel to
the outlet port on the top surface. A non-recirculation type of fuel feed system is employed in order to minimise
evaporative emissions. The feed pipe is routed along the LH top rear of the fuel tank bay to emerge through
the chassis beneath a plastic shroud, and thence into the engine bay. The pipe then continues without a joint
until connecting to the LH end of the engine rear bank fuel rail, to which the front bank rail is linked by a short
connector hose.
When the ignition is first switched on, the engine management ECU energises the fuel pump for a period
of about 3 seconds to prime the system before switching off. If a signal from the crankshaft sensor indicates
that the engine is being cranked or is running, the fuel pump feed will be maintained. The pump is switched
off immediately the ignition is turned off, or about 3 seconds after a stall. Note that after the ignition is turned
off, the ECU will remain live for up to 20 minutes (dependent on coolant temperature), to allow for heat soak
management (see sub-section KI.5).
A safety inertia switch is incorporated into the fuel pump electrical circuit, and operates in a severe impact
(indicative of a vehicle collision) to switch off the fuel pump feed and minimise the fire risk. The doors will also
be unlocked. The switch is mounted on the seat belt mounting frame LH backstay, accessible from the engine
bay, and is reset once tripped, by pressing the rubber button on the top of the switch.
An evaporative emissions 'charcoal' canister is mounted at the LH side of the engine bay bulkhead, beneath
the air intake duct, and is connected to the tank by a moulded tube. The plastic shroud covering the fuel pipes
in the cabin rear compartment, incorporates a removeable plate to allow access to the breather pipe connec-
tion to the tank. The purge port of the canister is connected to a solenoid valve mounted on the LH end of the
front bank cam cover, and thence to the intake plenum just downstream of the throttle body. The evaporative
emissions control system prevents untreated fuel vapour from the tank reaching the atmosphere, by absorbing
the tank vapour in a bed of activated charcoal in the canister. When the engine is running, the engine manage-
ment ECU opens the purge solenoid valve by duty cycle, and allows intake manifold depression to draw fresh
air through the canister via a third port on the canister, purging absorbed fuel from the charcoal, and consum-
ing the resultant vapour in the normal combustion process. In this way, the charcoal bed is 'cleaned' ready to
absorb more tank vapour when the engine is stopped.
Section LN
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