i know a few that have renewed glow plugs with the wrong ones(there are 2 types for the paj (green or black op iirc), also some cheap after market plugs have been known to come faulty, and not just 1 bad one, a full set!!!!
check your new plugs first, make sure they work, also check the condition of the main feed wire to your glow plugs and the bar connecting all the glow plugs is in good nick. also as above you need to see if the relay is working, check for how long you get feed to the glow plugs for (providing you can hear the relay click in the first place , a heavy clunk rather than a click)
hth