Single-acting flow valve

Location of the inertia switch (A) in the engine compartment

The inertia switch has the task of interrupting the electrical supply for the electric fuel pump if the vehicle undergoes sharp deceleration (impact) to prevent the fuel from escaping, if the fuel manifold or the supply pipe were damaged, and causing a fire.

The switch is made up of a steel ball fitted in a conical shaped housing kept in place by the attraction force of a permanent magnet.

Under the effect of the strong acceleration due to inertia forces the ball may be released from the manget and gradually come out of the conical housing with an upwards movement depending on the angle of the cone.

There is a rapid attachment mechanism above the ball which forms a normally closed (NC) circuit. When the ball is struck, the mechanism changes position to a normally open circuit thereby interrupting the electrical supply to the electric pump and causing it to cut out.

The calibration of the switch causes it to intervene for accelerations of more than 1.2 g (about 11.7 m/s², corresponding to an impact at a speed of around 25 km/h).

The switch can be restored by pushing the upper button protected by a flexible cover.

NOTE The inertia switch is fitted on the line between the coil for the pump relay and terminal 28 of the control unit (see page 8).

After an apparently slight impact, if there is a smell of fuel or leaks from the fuel system, do not turn the switch back on, but search for the cause of the problem and remedy it to avoid fire risks. If this is not the case and there are no leaks and the vehicle can be driven again, press the button to reactivate the electric pump.

SINGLE-ACTING FLOW VALVE

This is a safety valve fitted in the fuel return pipe near the tank.

The valve allows the return of the fuel into the tank preventing it, however, from flowing in the opposite direction if the pipe is broken.