Is there a lift pump for fuel that's failing? If you open the filler and let air in, does that help? If so, check the vent is clear
Just saw this when I did a search for your question:
Nissan Cabstar fuel pump problems
On the 3.0 L Diesel engine, one of the common Nissan Cabstar problems involves the diesel pump. The fault can cause a complete failure to start when it malfunctions.
You may experience power issues or fuel leaks that require repair as soon as possible.