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TR6 Inertia cut out [off] switch TR6


Senior Member
OK, went thru my first experience with my new TR6 not wanting to start. Turning the key everything worked, motor turned, no start. Again and again, and than realised I did not hear the fuel pump. DPO had installed an ingenious anti-theft system under the driver seat cutting the electricity to the fuel pump. Messed around with it, nothing. In the end it turned out to be a malfuntioning inertia cut out (or cut off) switch. Took it out, hotwired the cables and off we go. At home, took it apart (very easy) cleaned the rods, bend them into shape, installed it and like new.
As long long as the square magnet or the steel ball is not missing (unlikely, unless the whole casing went to pieces which si also unlikely to happen), this very hard to find item can ben easily made to work again.


Great Pumpkin - R.I.P
DNK said:
Which inertia switch was it?
The one only found on fuel-injected TR6 (meaning non-US-spec). Don't recall the TR6 location offhand, but on the Stag it's mounted to the firewall near the fuse block.


Great Pumpkin - R.I.P
DNK said:
OH, it's your Stag. Thought it was a 6
Er, no, sorry for the confusion. I wasn't the original poster, just (perhaps rudely ?) trying to answer the question. Jobster (the OP) was talking about his (fuel-injected) TR6.


Darth Vader
Hello all,

I don't think the Stag had an inertia switch, just the TR5, TR6 (injection) and the 2.5 P.I. saloons. This was to cut the fuel pump in case of an accident due to the 100+ p.s.i. fuel pressure which if a line was cut would be rather nasty.



Would a wire to the ignition lead on the starter and another to the 3rd post on the oil send unit (anti-run-on valve lead) work?

The starter lead would make it run when the starter is engaged and the oil send post should get it to run when there is oil pressure. The starter lead would need a diode to prevent feedback so the starter would not run when there was oil pressure.


Senior Member
It's the inertia switch to cut off the fuel pump in case of any mishap. You could do it manually as well if for any reason you need to switch on the ignition and don't want to have the fuelpump run in vain. It's mounted, at least on the TR6 PI versions, behind the main brake cilinder on the firewall.


Great Pumpkin - R.I.P
tomshobby said:
Would a wire to the ignition lead on the starter and another to the 3rd post on the oil send unit (anti-run-on valve lead) work?
Several problems with that approach, not least of which is that PI TR6 don't have the 3-post oil pressure switch.

Bosch actually made a cute pump-control relay, that monitored the ignition and shut the pump off if the engine wasn't turning. But I doubt it's any more reliable than the Lucas inertia switch (which seems to frequently show up used on flea-bay).


Great Pumpkin
Country flag
I have a ford style on my car,yet unproven, has some kind of a switch that cuts power on jolts and such.
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