The EFI Cub Cadets use a different kind of ignition key... it's a red plastic thing that looks at first glance like it just has a tip that fits into the keyhole and presses something in there when you start the engine. You might think it might be able to be replaced by just shoving a small screwdriver into the keyhole instead. But not so fast! The key turns out to have a tiny but VERY powerful little magnet which faces out to one side. It seems that when you push the key in, like pressing a button, the magnet at the side of the tip of the key moves next to a magnetic-type reed switch, pulling it, which then gets things underway. Why they chose this as the ignition key instead of a regular turn-the-key (including holding it 1.5 seconds) I don't know, but this seems to be how it works. You won't start the engine unless you have one of these keys, that's for sure.
The magnet on the key in this photo is facing down so you can't see it in the pic.
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