Its just as likely to be air in the system as faulty glowplugs.
Check your glowplugs to make sure they are working- use a multimeter to see if current is reaching the realy and then the plugs. You can also remove them one at a time and switch on and watch them glow if they are working. If you have a multimeter and know how to use it you should get a 1 ohm resistance from a good plug.
But it's just as likely to be air being sucked in- these engines will still start with only one or two plugs working: they'll chug and smoke a bit but still start, but you won't physically see air being pulled in. You need to check all the fuel line connections and also the injector and pump leak-off pipes for cracking.
The primer is well known for leaking and causing starting probs as well- especially if it's got a CAV bulb type one-have you pumped the primer for a while before starting?? If you do this and it fires up straight away then that'll discount the glowplugs.