The faster it cranks, the easier the diesel starts. If compression were low it would start hard (not as much heat from the compression). If it cranks faster, less time for the compression to leak down, more heat and more likely to start.

I wouldn't say this is necessarily an indicator of poor compression. If the car is left outside without a place to plug in, such as airports, a second battery isn't bad insurance. In the winter my father always kept one of the boat batteries in the trunk of his airport car for a jumper.

- Jeff Miller
190DT