My car wouldn't start one day, and I flattened the battery trying.

Then I borrowed my lodger's bicycle, got to within 1/2 mile of work, and collapsed in the snow, exhausted. (Yes, car exhausts too.) Took me about 1/2 hour to recover.
I realised on the way home that there was a very slight downhill gradient all the way.

The problem was, being believed. My job was to start the cars for the very first time, in the factory, as they were assembled. The other guys used to play tricks on me, crossing wires and stunts like that. It was hard to beat me.

(For the 'technical')
The problem with my Land Crab was a cracked cylinder head, between the combustion chamber and the inlet port. Back pressure in the inlet tract.