Non starting connect

[Flying Scotsman]

59 plate lwb connect. Approx 145000 miles. Van will not start, will turn over but not start,
Garage says problem will fuel pressure on low side. They say fault codes are showing for all four injectors and fuel pump, but that could be because there is no fuel getting to the pump or for the injectors to open/work. They removed fuel filter and only half full. They also had it running via a fuel bowser set up feeding the pump.

Any thoughts ??
TIA

[HST Doctor]

If it's running with a fuel supply straight to the pump, there isn't too much wrong with the pump and injectors. Could be the low pressure section of the fuel pump not drawing the fuel from the tank. Other possibilities are air being drawn in between the tank and the pump, I recently had a problem and changing the fuel filter and the non working glow plugs cured it, this wasn't giving a fault code on my reader initially, but finally it did throw up a low fuel pressure fault as when cranking the pressure just kept dropping as the fuel starvation occurred.