Hello guys, boy do I need some help here please...

2001 Courier van 1.8 Tdi.

Tuesday night did 20 mile trip with no problems. Weds night and it will not start at all. Glow plug light starts flashing if you crank for any length of time. Did start it 3/4 times out of 30 odd attempts BUT it won't catch.

Fuel filter new two weeks ago
Cracked injectors and fuel getting to them
Cracked banjo inlet to pump and fuel there too

Error code p1664 shows which kind of suggests low fuel pressure and possible air leak in the fuel delivery system?

Any help appreciated as I am tearing my hair out.

Thank you.