First off, I'd check all the terminals for any corrosion
, especially the grounding circuit. Even with a good battery
and positive if it can't get back to the battery
it's a no go.
Second, you could remove the starter motor
, just 2 bolts, and see if the battery rolls it.
Also, in the time of activity if there was any moisture in the cylinders there may be a tiny layer of rust at the ring edges. Can you roll the engine
over with a socket and breaker bar? .. Pull the injectors and put a little diesel
and lite oil
mix into the cylinders and roll it over with a breaker bar to clean the cylinders.