What would cause a W123 1979 300D diesel to NOT FIRE at all, after changing glow plugs?
Glow plugs are reinstalled and the electrical series correct according to glow plug wiring diagram.
Other factors are that the glow plug light stays on about a minute too long, causing the serial connector wires to turn red hot. Also, after the glow cycle, the light goes off, and then about 30-45 seconds later, the relay terminates power and the wires stop glowing red. When the ignition switch is turned over to "start" the glow plug light comes back on again, but the engine does not start.
While the engine would at least fire before the glow plug change, now it just cranks and no ignition at all.