Was it filled with diesel #2? or gasoline?
What's to say the problem is fuel related?
It may not be.
But let's say it is for this test. At the injection pump crack loose one
or two of the high pressure lines to the injectors to see if fuel oozes
from the intentional leak when the motor is cranked. If so, the motor
has fuel, if not, why not. Don't over tighten these lines, just snug
enough to not leak.
If no fuel at the injectors I'd check all the hose connections and
filters that you've disturbed for tightness - an air leak may be the cause.
Then I'd check the shut down device - if it is vacuum powered, does its
vacuum line have any oil in it? If so the device is broken and may be
holding the fuel rack in the OFF position.
These 3.5L diesels have a spotty reputation.
Has this 3.5L motor "acted up?" burned oil? made odd, grunting noises?
Hopefully not, but if so, there may be serious problems - with bent
connecting rods and scored cylinder walls often #1 and #4.