When you turn the key on, the fuel solenoid should make a very audible click, and if you notice the position before and after, it should be noticeably different. On a diesel, the only way to kill the engine is to cut the fuel, so any problems with the fuel solenoid is a bad thing. You can also break a fuel line fitting loose and crank it, and you should be getting fuel spraying. Often if you ran out of fuel, had a broken fuel line, or even if it's sat for too long, it may just need to be primed, which can usually be done with the manual priming pump on the side of the injector pump.