APRILIA ATLANTIC 500, Workshop Manual

Page: 67 / 170

Fuel system
chap. 4
4-2
Release 00 2002-09
Atlantic 500
FUEL PUMP AND TANK
EMS FUEL INJECTION SYSTEM
This fuel injection system has integrated injection and ignition.
Injection is indirect into the manifold, using an electronic fuel injector.
Injection and ignition are phased to a 4-stroke cycle, using a phonic wheel dropped on the camshaft control and a
reluctance variation sensor.
Carburation and ignition are both controlled according to engine revs and gas valve opening.
Further corrections are made according to the following parameters:
- Coolant temperature
- Intake air temperature
- Ambient pressure
The system corrects the idling supply with a cold engine using a stepper motor, which is inserted into a by-pass
circuit of the gas valve. The control unit controls the stepper motor and the fuel injector opening time, thus guaran-
teeing idling stability and correct carburation.
Carburation is controlled in all operating conditions by modifying the opening time of the fuel injector.
Fuel supply pressure is kept constant according to ambient pressure.
The supply circuit is comprised of:
- Fuel pump
- Fuel filter
- Fuel Injector
- Pressure regulator
The pump, filter and regulator are inserted into the fuel tank on a single support.
The fuel injector is connected by two pipes with snap-on couplings. This forms a continual circuit that prevents the
risk of fuel boiling. The pressure regulator is located at the end of the circuit.
The fuel pump is controlled by the EMS control unit; this guarantees vehicle safety.
The ignition circuit is comprised of:
- High tension coil
- High tension cable
- Shielded cap
- EMS control unit
- Spark plug
The EMS control unit controls the ignition with optimum spark lead and at the same time, guarantees the timing of
the 4-stroke cycle (ignition only during the compression stage).
The EMS fuel injection-ignition system controls engine operations by means of a pre-set program.
In the event that any input signals are lacking, acceptable engine operation is in any case guaranteed in order to
allow the user to reach the repairs workshop.
Of course, this is not possible when the stroke-revs signal is lacking or when a malfunction occurs within the control
circuits:
- Fuel pump
- High tension coil
- Fuel injector