Fuel pump cut-off

[ATE399J]

Hi all,

Having (several years ago now) converted to run with an electric fuel pump I've always meant to install a cut-off switch that would kill power to the pump in the event of an accident. They seem to be pretty standard on modern cars (I know my Ka has one anyway - and you don't get much lower tech than that).

I have trawled through most of the usual sites but have yet to find such an item designed for after market fitment. What have those of you with electric pumps done?

P.

[Adrian@]

Alternator run relay with diode is standard fitting on Turbos....and as I fit to all electric pumps, and you can if you want add prime switch too.
Adrian@

[ATE399J]

Thanks Adrian, very clever - and simple! (Where's a Merecat when you need one!)

P.

[thegamekeeper]

They are called fuel pump inertia switches. Plenty on ebay. Buy one with reset button and you can use it as an antitheft device. Flick it and it will deactivate pump. Reset and it starts. Simple but cleverer than the average car thieving scrote

[Adrian@]

ATE399J said:

Thanks Adrian, very clever - and simple! (Where's a Merecat when you need one!)

P.

If you need the wiring diagram or kit PM me ..if the pump is already powered by a relay then power that relay via the alternator warning light (NY) and ignition key turned (WR) with a diode between the relay and the WR wire, this will power the relay during cranking. THEN add a switch to kill the link to the pump OR a 12v switch to the relay for a prime.
Adrian@

[thegamekeeper]

Adrian@ said:

ATE399J said:

Thanks Adrian, very clever - and simple! (Where's a Merecat when you need one!)

P.

If you need the wiring diagram or kit PM me ..if the pump is already powered by a relay then power that relay via the alternator warning light (NY) and ignition key turned (WR) with a diode between the relay and the WR wire, this will power the relay during cranking. THEN add a switch to kill the link to the pump OR a 12v switch to the relay for a prime.
Adrian@

Not sure how that cuts the fuel pump feed in event of accident. Surely all it does is maintains 12v supply to pump while engine cranking. In event of accident, if engine still running or ignition still on fuel pump will continue to pump unless you switch it off with your "kill switch".

[Adrian@]

Steve, the pump relay is held in by the alternator, the engine stops and the diode limits the feed to the starter wire, on ignition cranking the relay is fed via the diode to the relay....IF you have a fused feed to a relay running the pump then the cost is about 4 pence ...IF you need a relay and a fuse holder then a million pounds.
Adrian@
Of course you could still crash the car and have the engine running...that said you could crash the car and assume that an inertia switch has tripped and it's not.

[thegamekeeper]

I must be missing something here but I,m sure you just described what I said. Phil obviously has a relay and a fuse so a million pounds saved there (by the way I know where you can buy them for less than half that!). What he wants is an inertia switch to turn off fuel pump in case of accident, £10 ish. Yes of course they can fail, so can the brakes but its not a good enough reason not to fit any, alhough I,ve never known it but if you "flick" it off now and then you have a good idea if its functioning properly.

Edited by thegamekeeper on Tuesday 11th October 18:00

[Adrian@]

BARGAIN get 2....the biggest problem is it confuses electricians that cannot hear the pump running once the ignition is switch on ...as this system only holds the relay in at cranking or alternator running.
Adrian@
BUT by pulling the alternator plug with the ignition on it will prime dry lines IF you don't have a prime switch.

[thegamekeeper]

So just to sum up, dont fit the thing you originally asked for in case it doesn,t work (which it will) and it may confuse an incompetant electrician. 2 perfectly good reasons to fit something you dont need and dont really want. BUT, PLUG and DRY lines are things of which I have no experience. Off to feed my Merecats, good night

[ATE399J]

Thanks for all of the advice and information guys, I can see both sides of the arguement (honestly).

I already have the pump on its own key switch so can disable it, if you drive off forgetting you get exactly 20 yards (not that I've ever done it).

I've searched flea-bay and found one sold for a Landy and it'll do exactly what I want, sorry it's not exactly TVR original.

I'm surprised that I couldn't find such an item through Demon tweeks etc. - thought they'd be a 'must' for racing, I guess they have something far more sophisticated.

Anyway, thanks again for your time and experience.

P.

[Gnasher]

I used one from Rimmers on the V8M I built, a TR6 part if I remember correctly, and put it on the inside wing.

I did use it as an anti-theft device, just pop the bonnet & flick it up, no power to the fuel pump, that and a discarnet were cheap, if not infallible anti theft devices.

SteveD