The glow plugs are a simple necessary circuit.
Its sounds like it is an open circuit now. When replacing the glow plugs care has to be mantained to keep the buss bars and insulators mounted properly. A short to ground before the number one plug will cause a breif current surge which will burn a new plug in an instant. You need either professional help (I would charge $30 to diagnose this simple system and then only as a minimum shop labor charge - in the time it takes me to write this I could diagnose 4 of you systems) or you need to get the wiring diagram and a couple tools and learn how to test.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician