MG Car Repair: Valve engine run on, e mail address, inline fuse

Question
I have a 1976 MG midget. And have pretty well rewired the whole car except the engine run on valve. I know there should be power to the valve but am not sure where it connects. A lot of the old wires were just cut out which I had to sort out. This valve has two wires to it but both cut off. Any help would be appreciated.
Doug

Answer
Hi Doug.  The cut-off valve is just a spring-loaded air valve which is held when the ignition is switched on.  Originally, this valve had two wires attached to it, one grey and the other grey with a yellow stripe.  

The grey wire was powered via an inline fuse directly to the 5th terminal on the ignition/starter switch that is live when running AND when starting.  Note that the regular accessory fuse is not powered whilst the starter is operated.

The Grey/Yellow wire was an earth return that was routed via an oil pressure sensor.  In theory, if you lost oil pressure then the engine would cut out to preserve the engine from damage.  This also means that the engine will not fire up until the starter motor has generated sufficient oil pressure to operate the switch. Personally, I would route the Grey/yellow wire directly to earth.  

Send me your e-mail address in another question (with privacy turned on), and I will send you a copy of the wiring diagram.