Since the machine starts the issue is pretty much moot but, my understanding is that most Cat glow plugs of that era draw 5 amps each. If the machine has a working amp meter it should indicate 5,10,15 or 20 amps discharge depending on the number of plugs working.
You only need two tools in life - WD-40 and Duct tape. If it doesn't move and should, use the WD-40 If it shouldn't move and does, use the duct tape.
Cat D4D 83J w 3304 PC engine, FOPS, s/t blade, D4F winch, air ride seat, "wobble" stick blade lever and D8H control panel