Make sure engine is turning over at a good speed. I had a situation where the engine turned over slow because of an alternator that locked up. This slowed the engine cranking speed down enough for a no start.

When you turn the ignition switch to the run position does the glow plug light blink. This would let you know that there is an error code stored in the VW controller. You would need to get a laptop with the Linde Pathfinder program hooked up to the truck and get the codes out.

Check for power at the fuel cut off solenoid on the injection pump.

Do you have fuel squirting out of the injection lines if you loosen them up at the injection nozzles and crank the engine over?

Was this a situation where the lift truck engine died, or it did not start after a normal shut down?