You didn't say which engine.
If it has a 2.8 or a 3.1, there is a technical service bulletin out on
these, whereas the crank sensor gets oil in it, rendering it inoperable.
Then, when you go to start it, the ECM doesn't fire the ignition and/or
the injectors since it doesn't "know" the engine is cranking.
Does the tach move while you're cranking it??
You can check the crank sensor resistance (static) as well as output
(during cranking) to see if it's out of range.
Anyone know the specs?
You need an analog meter to check the sensors voltage while cranking.
Mine did that ('89, 2.8) and I got out cheap as I had a donor car to
rob the sensor off of--otherwise they're rather spendy.
Then after overwinter storage it wouldn't start again, and I unplugged
& blasted the connector pins on the sensor and it fired right up.
That's probably all it needed the first time it acted up.
According to the TSB, many come into the shop and will start again
after replacing the crank sensor, although the old one they discarded
was likely still good.
Super easy to change, one bolt and it slides right out. As such, you
could possibly rob one from the junker, but it's unlikely you'd know for
sure it was good. Maybe first just unplug it and blast the connector
with electronic cleaner.
Anyway, it must be a common problem, I can vouch for that as it's
happened twice with two different sensors.
BTW, now it's a ritual every oil change or two, unplug that connector
and blast it with electronic cleaner.