so it turns over fine but won't fire??
could be neutral safety switch is on the fritz, maybe the ecu is throwing a bad code then once the battery dies it resets itself??
You have fuel injection so it could be an electronics issue, if you smell fuel coming out the exhaust its a spark issue I would guess, Maybe take it to a mechanic and see if they can find a bad code that needds to be fixed or something
the low idle would indicate an electronics issue IMO, its controlled by the ecyu so isf that was OK why would it be normal for most of the time then 500 at other times?? fuel pressure also like Peter said maybe??
Wish they put Ford motors in sangers then I would never worry about mine
not that I really do anyways