Could be your Cam Position Sensor just happened to go out after your stop. Mine went suddenly after driving fine. Had very similar symtoms, my car would crank like crazy try to start when the battery got low then pop as if a back fire just as you described. I have a 94 850 Turbo. Popped in a new Bos...

Ordered a Cam Position Sensor (Bosch) put it in - Bingo. Hope this helps anyone out there with a similar problem.
Car's running great.

Just glanced at my orig post - forgot to say its a 850 turbo, had the turbo replaced about 5 yrs ago

Thanks for all the posts, tried the holding pedal down as if it was flooded, no go. Its getting spark OK.
Checked the fuel pressure with a tire gauge - it was only about 18 or 20 psi, guess I should check the filter and
regulator where ever they may be....

1994 850 140K miles - starting and running great and then out of the blue, won't start, cranks like crazy. New fuel pump about 2 years ago, can hear it prime and smell the gas. Haven't checked the plugs yet but what's odd is that when the battery gets down to barely cranking it almost starts. Small ...