Inertia cut off switch.

[Ken F]

Hello,

my TR6 is a 1970 and was never fitted with an inertia cut off switch. 
 

Originals  are hard to find I’m told but I’d rather have a modern reliable one. 
 

which one should I buy?

where should I buy it?

Is there a technicality on fitting and wiring?

Anybody who’s done it got any tips?

I drove to the Dordogne in ‘91 with my little boys strapped in the seats I made and to the internationals in the 90s. Makes me shudder to think. 

petrol wasn’t so volatile back then I suppose.

regards Ken. 

[Trev Good]

MG owners club sell one of the best ones and at a price lower than most distributors. I've bought quite a few from them for my electric fuel pump cars. They sell to anyone, look on their website:-

mgocspares.co.uk/product/e013/inertia-cut-off-kit

Fitting is easy....it should be upright on the bulkhead and wired into the fuel pump live circuit.

[Ken F]

11 minutes ago, Trev Good said:

MG owners club sell one of the best ones and at a price lower than most distributors. I've bought quite a few from them for my electric fuel pump cars. They sell to anyone, look on their website:-

mgocspares.co.uk/product/e013/inertia-cut-off-kit

Fitting is easy....it should be upright on the bulkhead and wired into the fuel pump live circuit.

Thank you,

should I fit one on my wife’s mgbgt when/if I get it back on the road?

Ken

[Firefly]

 

            MGOC are out of stock. Plenty on the bay, bought mine off there, half the price, its not something that wears out is it, and of a car that had it fitted in the factory. 

[stuart]

9 minutes ago, Ken F said:

Thank you,

should I fit one on my wife’s mgbgt when/if I get it back on the road?

Ken

As it has an electric fuel pump then yes its a good safety feature.

Stuart.

[john.r.davies]

The switch sold by the MGOC is used by many modern manufacturers, from Citroen to Jaguar to Maserati!  Which has to be a recommendation.

It may be worth noting that while the switch has three terminals, they are sold with a connector that uses only two.   If the switch triggers, it disconnects the first two  and connects the third, so that a warning light can inform you that it has been an impact that has caused your engine failure!   Useful if, say, you run a kerb!     Adding an extra wire to the connector should not be a difficult task.

John

[Ken F]

Thank you all for your replies. 
 

great. 
 

Ken 

[Hamish]

I use the red top type like this

 

https://ebay.io/m/YEQjAS

 

you just need to satisfy yourself it suits

[StevecTR4]

Interesting to hear where on the car, they are generally being fitted.

I have installed one in the boot of a TR4A as a quick fix until I decide on the best long term option. Inserted the switch inline with the pump power supply.

It came as a kit with indicator light from a main supplier

[Ken F]

27 minutes ago, StevecTR4 said:

Interesting to hear where on the car, they are generally being fitted.

I have installed one in the boot of a TR4A as a quick fix until I decide on the best long term option. Inserted the switch inline with the pump power supply.

It came as a kit with indicator light from a main supplier

That’s good to know, I thought why not put it on the boot between the pump (Lucas) wiring. 
Ken

[Tim T]

I bought a used LandRover one for the 5 for about £12 on eBay. Fitted it near the wiper motor where a 6 one would be.

Tim

[Schnippel]

Hello,

It's usually mandatory to operate electric fuel pumps only with a fuel pump relay.

At least that's the case in Germany.

This means the pump only runs when it receives a signal from the ignition.

I install it this way on every TR with an electric pump.

Best regards,

Ralf

[RobH]

No relay mandatory here Ralf except perhaps on new cars, but all cars with an electric fuel pump have it ignition-switched.  You wouldn't want it powered when the engine isn't running.    

It is a good idea to have a relay though,  as it means less resistance in the fuel pump supply and saves the ignition switch from having to carry the pump motor current. 

[Ken F]

3 hours ago, RobH said:

No relay mandatory here Ralf except perhaps on new cars, but all cars with an electric fuel pump have it ignition-switched.  You wouldn't want it powered when the engine isn't running.    

It is a good idea to have a relay though,  as it means less resistance in the fuel pump supply and saves the ignition switch from having to carry the pump motor current. 

Thank you Ralf and Rob,

I fitted a relay when I did the wiring mod with updated wire, the wires in the boot used to get hot. 
great improvement. I believe the mod is in technicalities or whatever it’s called. 
 

should a cut off switch be before the relay or after?

Thanks Ken 

[RobH]

45 minutes ago, Ken F said:

should a cut off switch be before the relay or after?

I don't think that really matters Ken - either way it cuts off the current completely.   Which ever is most convenient for making the connections would seem sensible. 

As what could be viewed as a safety-critical component, I believe it should be in the main power feed to the pump and not just in the feed to the relay operating coil.