if glow plugs are duff or not fed with current it will still start eventually just take ages to do so
106 diesel starting problems most common of 2 things
air in the fuel from a leaking vacuum pump housing (bit with the plunger on)
or the fuel solenoid shut off valve is stuck or immobilised
just a thought - he's not run out of fuel recently has he
if so it will take ages to get it back through