A quick and easy way that will immediately determine if diesel fuel is being injected into the cylinders, is when the engine is cranking-over while cold, there will be little puffs of dense white smoke coming out the exhaust pipe. The throttle has to be opened up about half-way to make sure a good amount of fuel is being injected to make smoke, the smoke being unburned fuel.
Another way is to unscrew one of the retaining nuts from one fuel injection line going to a fuel injector. Once the retaining nut is loosened, crank the engine over. Fuel will be squirted out from the loosened injection line connection, the squirts will come out in pulses, not a steady stream, the pulses correspond to the power strokes of the cylinder the injection line goes to. If there aren't any little periodic squirts of fuel coming out of the loosened connection, then the problem is in the fuel deliver system somewhere. Don't forget to tighten the nut back down, and DON'T over tighten it.