1984 300TD Wagon. All of a sudden, we have no glow plugs. The dash light isn't illuminated and the plugs aren't getting hot. We thought we had tracked the problem to the preglow time relay, and changed it out, which includes the 80A fuse, but the problem still exists. Any thoughts?

 

I fyou have a ohm meter test the relay plug to the glow plugs could be the wire harness or bad ground?
any ideas on how to test the starter/solenoid on a 300sd

 

If you have one GP out, the light will work perfectly, if you have two... nothing. Because of the way the plugs were wired together from the factory, if #5 is out, no other plugs are getting power because of the circuit. but if you have a problem with #1 the 4 others will receive power just fine. With the ohm meter comment, exactly, test them. Multimeters can be picked up at any sears or hardware store generally. It is never a bad thing to give yourself some new plugs and rewire the circuit check out diesel giant for these parts and tips on how to get yourself back on the road. Good luck!