You can "jump" a car without the donor cars engine being on. Just needs a good 12v source and similar CCA to crank. I could be wrong though.

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1973 - Porsche 914 1.7 Stock - Sold (sad day)

2001-VW Beetle 1.8t Modified (200HP) - Lost my "man card"

2002 - X5 4.6is - Stock - Got my "man card" back