BMC Engine Run-on Cure

My Yellow MK1 Sprite has a 1330cc high compression engine and has always suffered badly with engine "run-on" when the ignition was turned off. It was so bad that the whole car would shake and the engine "knock" for a second or two.

I used to leave it in gear and let out the clutch when switching off. Then one day on the internet looking at an Austin Metro 1275cc I saw a valve mounted on the intake manifold. A bit of research revealed it was an "anti run-on" valve. The valve is energized when the ignition is switched on and closes. When the ignition is switched off the valve opens and allows atmospheric pressure into the intake manifold. This creates the same pressure both sides of the carburetor, thus no fuel is drawn into the engine and it stops running immediately.

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