My 87 300d keeps blowing the 80 amp glowplug relay. Is this my relay or is it something else. The only thing I did was check the glow plugs from the relay plug. and the plug will only go in 1 way.
Anyone got some suggestions for me?

Check the continuity of the glow plug harness wires between the glow plug end and the relay plug to see if one of the wires has shorted out against something. The insulation on one of the wires may have rubbed off with the engine vibration......probably a good place to start.
Cheers

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FRED

Daily Driver: 98 E300TD 199K
Hobby Car: 69 Austin Mini
Past Diesels: 84 300SD, 312K
87 300SDL, 251K
94 Chev. K-1500 6.5Ltr.TD, 373K

I checked the wires and plugs they were all good. I don`t know how to test my relay.

What was the ohm readings on each plug from the plug body to the wiring tip?

You can leave the GP harness unplugged from the relay, just leave the control wiring on it, and try it, if the fuse remains, the relay isn't shorting out, it's somewhere in the plugs or harness to the plugs. Next, disconnect the harness from the plugs, make sure the ends do not touch anything, plug the harness to the relay and try it, if fuse remains harness is good and plugs are the culprit. Hook one wire at a time to the plugs, the one that pops the fuse is the bad one. Check them all as there could be more than one bad.

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Chris
64 190D R.I.P.
80 240D W/617 engine -for sale
82 240D -for sale

I am a stupid,stupid,stupid man.
When I tightened the wire up on the glow plug it laid up on the intake. It seems like it only happens when you get in a hurry. Now I will have to wait until the fuses come in that I ordered..Noone in this area carries them.

Eh...we all have our off days, things happen. I take it either the test method worked or you just happened to spot it...

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Chris
64 190D R.I.P.
80 240D W/617 engine -for sale
82 240D -for sale