Where does the inertia cut switch fit in?

Triumph PI inertia switch circuit diagram

The inertia switch is a vital bit of safety kit. If the car crashes the sudden jolt should turn the power to the fuel pump off. I have read of people leaving this component out of their systems but think that is just mad. Would you want the high pressure fuel to keep pumping if the car crashes?

The switch was fitted to several Triumphs including Stag, TR5, TR6 and 2500PI (and some other cars such as Jaguar and MG) so it is not to hard to find. There are new style modern inertia switches available.

Triumph Inertia Switch in bits

It easy to take apart and clean up the contacts. A while ago I borrowed this image from a Triumph Stag site and unfortunately have now forgotten - if it your image let me know and will and add a credit to you.

Modern Inertia Switch

If using a modern inertia switch bring the power to the C (common) and the output to the fuel pump relay from the NC (normally closed). The NO (normally open) side can be used to activate a lamp on the dash to indicate that inertia switch has been tripped. In the "tripped" condition the NC side goes open and cuts the fuel pump power and the NO side closes and lights the warning lamp if fitted.

Another modern inertia switch