Outer Limits 4x4 Board

I have seen diagrams showing how the Schrader spark-plug tyre inflators work without filling your tyre with a perfectly explosive mixture of fuel and air, and I can't understand how they work. Does anyone? Can someone point me to a website somewhere?

they pump air into your tyre. You take your spark plug out, screw the adaptor in and then un the engine (roughly I'd imagine) and the air that is normally compressed with the fuel mixture is expelled out instead.

grimbo wrote:they pump air into your tyre. You take your spark plug out, screw the adaptor in and then un the engine (roughly I'd imagine) and the air that is normally compressed with the fuel mixture is expelled out instead.

so, wheres the fuel go??

on the other side of the piston... lol

macca81 wrote:

grimbo wrote:they pump air into your tyre. You take your spark plug out, screw the adaptor in and then un the engine (roughly I'd imagine) and the air that is normally compressed with the fuel mixture is expelled out instead.

so, wheres the fuel go??

The theory (as I understand it) is that the engine is only idling, so manifold vacuum is significant. The cylinder sucks air in through the adaptor rather than air/fuel through the inlet valve, so the device only pumps air.

That's my understanding, too. I have seen diagrams of how it works, but they are notional representations, not technical diagrams. There must be some kind of valve in that screw-in device, but I can't imagine how it is manufactured.

I had one about 15 years it worked great.

The air comming out never smelt like fuel

It was mainly used after beach travel. The only draw back were
- the little valve unit got realy hot and took ages to cool down
- removal and reinstall of the hot spark plug