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Lotus Service Notes Section EMN
Page 20
Fuel Pump Switching
The fuel pump is controlled by the ECM via the fuel pump relay located in the relay module, and is
energised under the following conditions:
. When the ignition is first switched on, the ECM grounds the pump relay coil for a few seconds in order to
pressurise the fuel rail, and then switches off.
- When cranking, the ECM receives an engine speed signal and operates the pump continuously.
- When the engine is running, the ECM receives an engine speed signal and operates the pump continu-
ously.
- If the engine stalls, the ECM will switch off the pump after about 10 seconds.
- A safety inertia switch is mounted ahead
of the ECM, and controls the supply to
the fuel pump relay. Vehicle impact will
trip the switch and isolate the fuel pump.
Reset by pressing the button on top of
the switch.
Fuel Rail and Pressure Regulator Valve - Testing
The single fuel rail is used to link the four port injectors to provide a balanced fuel supply at common
pressure, and also to retain the port injectors in the inlet manifold. The left hand end of the fuel rail receives
fuel from the in line filter, and the right hand end houses the pressure regulator valve, from which fuel returns
to the tank. The fuel pressure regulator is a diaphragm operated relief valve with fuel pump pressure acting on
one side of the diaphragm, and regulator spring pressure and intake plenum pressure on the other. The
Fuel filler neck Filler breather
hose
Fuel filter Fuel pressure
regulator valve
Fuel tank
Fuel pump
Fuel rail
Fuel injector
Fuel feed line
Fuel return line em208
Inertia
switch
ohs1