Engine runs, even after switch master cut off

[mopetta]

Today i drove some 50 kliometer with the austin seven, long time in heavy rain.
When I tried to stop the engine, i first switches off the ignition, nothing happened. So I switches of the master cut-off key, nothing happend…

Any ideas what could have happend that the engine did not stop?

Thanks, Oliver

[Tony Betts]

Is this a mag engine.

Tony.

[Mark R]

If the cut off switch is switching everything then the dynamo may keep the coil ignition working, as Tony suggests if it's mag ignition they rely on you grounding the magneto so a wire may have come loose?

[Tony Betts]

This is your mag switch.

It's a simple pull / push, on and off.

   

[Stuart Giles]

To kill a coil motor while the dynamo or alternator is charging you need this type of Master switch. https://www.ebay.co.uk/itm/232365492403?...Swo4pYMD-G
The two extra pairs of terminals provide a separate 'break' contact pair for your ignition or dynamo D lead. The other pair is a 'make' for installing a pull down resistor or diode to stop a voltage spike killing the sensitive electronics on modern cars.

[mopetta]

Thanks for your feedback. Its a coil engine. The ignition switch is connected to a relay the switches the power of the battery. The master switch is one like the ebay link shows but only disconnects the battety plus from everything else

Best regards
Oliver

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I attached the schema for the electrics. I use the Lucas switch to switch the water pump on/off, not to switch the ignition.

   

[Reckless Rat]

The ignition on my coil engine is switched, but without a relay. I had to by-pass the Lucas PLC switch many years ago and now have a separate switch under the dash. It has worked fine for many years so I wonder if your relay has stuck.

[John Mason]

My battery isolation switch is between battery negative and earth very near to the battery terminal. All works well cuts power to everything when switched and stops the engine. No fancy relays. I don’t know if this would work with mag engine though.

John Mason.

[Bob Culver]

And I have been tellng everyone Seven wiring is simple! Can see the knochen will knock off the volts but cannot fathom the rest. Can anyone explain please?

Coil cars continue to run with the battery disconnected. But the system voltage likely goes far above 6v and will damage bulbs and maybe the coil. Might even start if run downhill.

[John Cornforth]

Hi mopetta

As the others have said, the generator continues to supply voltage even if the battery is disconnected, and this is supplying the coil ignition and keeping the engine running.

I recommend a separate on/off switch in series with the supply to the ignition coil. You could hide this under the dashboard as a security measure.

Why did you change the original ignition switch so that it controls the water pump ? - This is rather unusual.