TR6 Fuel Cut Off switch

[nmarston]

My inertia fuel cut off switch on my TR6 has died. Neither Moss or Rimmers suppy them any more. I've wired round it to get the fuel pump going again. Any one know where I could get one or if not whether wiring round is a safe idea???????

thanks

Nick Marston

[Steve AKA vitessesteve]

You can get modern fuel cut off switches, try your local car parts provider.

Or, originals come up on eBay every now and then.

The car will work fine without the switch, just do not have an accident.  High pressure fuel being pumped out of a broken fuel line does not bare thinking about.  

There are other Triumph specialists who may be able to help such as Canley Classics or Jigsaw.

I expect the various TR specialists such Revington and TRBitz could sort you out.

Also see http://www.club.triumph.org.uk/links/links.htm

Have just remember that Jasoin Chinn used a modern replacement http://chinn.blogspot.com/2006/06/maintaining-inertia.html

[Richard B]

If you're  running the pump through the swtich then the current will eventually burn out the contacts.

This is another area where a relay switching the pump will help things. You can use the switch on the earth path of the relay.

[Steve AKA vitessesteve]

To run via a relay wire it up like this: http://www.vitessesteve.co.uk/PI_Project/PI_Project3.htm

[piman]

Hello Nick,

the switch can be dismantled and cleaned up so it will work. Good old simple engineering.

Alec

[stagnant]

piman wrote:

Hello Nick,

the switch can be dismantled and cleaned up so it will work. Good old simple engineering.

Alec

Nick

Absolutely right - just take it apart, clean the contacts and it will last another 30 years!

[Jason]

The original inertia switches come up on eBay quite regularly, they were standard equipment on Stags too. Modern ones are less than a tenner and the second hand original types seem to fluctuate between 5 and 15 quid depending on which way the wind is blowing (prices inc postage).
I kept a spare new one, must find it and put it safe so I can't find it again :-)

[stagnant]

Jason wrote:

, they were standard equipment on Stags too.

Also, some Jags and L-Jetronic Alfa Spiders of the same period - probably many others

[BarryH]

You can't get new ones and the ball in mine on the Stag was thoroughly corroded and although I think it now works I don't trust it.

I am also not convinced they provide much protection unless you roll it but I am willing to be corrected.

Is there any reason why simply joining the spade terminals together is not recommended other than the loss of the switch of course.

[stagnant]

bhuffer wrote:

You can't get new ones and the ball in mine on the Stag was thoroughly corroded and although I think it now works I don't trust it.

I am also not convinced they provide much protection unless you roll it but I am willing to be corrected.

Is there any reason why simply joining the spade terminals together is not recommended other than the loss of the switch of course.

A sharp impact will do the trick, it doesn't need to roll. You should consider the consequences of being trapped in a wrecked car with fuel still being pumped at 100+psi. If you fancy a Viking funeral, then go ahead and join the terminals together!

[Richard B]

bhuffer wrote:

I am also not convinced they provide much protection unless you roll it but I am willing to be corrected.

I managed to trip mine in the Spitfire by hitting a bump 'to hard' at about 30mph.

[BarryH]

Thanks for the responses and for fuel injection and the fuel pressures involved I can understand the need for care but in the Stag with its carbs the pressure is a lot lower.  With regard to the road bump, the vertical shock was obviously enough but if you look at the picture of switch the ball is retained between two metal strips and the tube only allowing vertical movement.   So I don't see how anything other than a roll over or something that simulates vertical movement can make them work.  If somebody can give me the part number of a modern switch I would certainly get one as I understand they give more all round protection.

[SteveJP]

Hi Barry

Must admit - mine in the Stag was bypassed by a previous owner - it's still there on the inner wing, but the terminals are patched together, presumably at some point it was giving trouble. Must admit, I haven't given a thought about replacing it. (wait for flak!)

[stagnant]

bhuffer wrote:

  With regard to the road bump, the vertical shock was obviously enough but if you look at the picture of switch the ball is retained between two metal strips and the tube only allowing vertical movement.   So I don't see how anything other than a roll over or something that simulates vertical movement can make them work.  If somebody can give me the part number of a modern switch I would certainly get one as I understand they give more all round protection.

It's all to do with kinetic energy, rather than gravity - the heavy steel ball is put in motion by the abrupt change in velocity and activates the plunger. Try holding one upright and giving it a sharp jolt or whack on the casing - the plunger will readily disengage.

Moss supply a replacement modern version of the inertia switch. I've seen one listed either in their TR6 catalogue or on their website.

I agree, it's much less of an issue with the Stag with low fuel pressure, but a useful safety device nonetheless as petrol fires take hold very quickly.

[gilesdive]

I have tried jolting mine when I had it loose in my hand, and it works, it does spring up.

I also tried rolling it over once, and if you do it smoothly, it will not cut off the petrol. It's the jolt that does it. (By the way, when I rolled it over, it was in the car at the time.  oops.). Also the fuel pickup is no longer under the level of the petrol when you are upside-down, so it won't pump much anyway.