Timing sensor (sfa 200)

NOTE Sensor angular position may not be adjusted in any way.

TIMING SENSOR (SFA 200)

The I.A.W.-1AF.13 system adopts a phased, sequential injection system. In other words, fuel is injected into each cylinder in sequence during the intake phase.

To achieve this, the ECU uses a timing signal together with the rpm and TDC signal to determine the point of injection.

This signal is generated by a Hall sensor fitted on the exhaust camshaft pulley.

Principle of operation

A semi-conducting layer with current flowing through it is placed in a normal magnetic field (force lines at right angles to current direction). A potential difference known as a HALL voltage is set up at its terminals.

If current intensity remains constant, the voltage generated depends solely on the intensity of the magnetic field; magnetic field intensity need therefore only vary periodically to set up a modulated electrical signal with frequency proportional to the speed with which the magnetic field changes.

To achieve this change, the sensor is crossed by a metal ring (internal part of pulley) with an opening. The moving metal part of the ring covers the sensor and blocks the magnetic field to produce a low output signal. The sensor generates a high signal when aligned with the opening, i.e. with magnetic field present.

The alternation of signals is therefore dependent on the succession of openings (see chapter on "signal management").

Removing-refitting

To gain access to the timing sensor, remove the intake side camshaft pulley (3) (refer to engine service manual, publication no. 504.589/20).

Disconnect electrical connection of sensor.

Unscrew both screws (1) and remove timing sensor (2) with retaining plate.

1. Deflector
2. Magnetic material
3. Gap

Wiring connector

The numbers in boxes indicate the corresponding control unit pins