Glow plug stumper of the week

[anhydrous7]

This thread involves my 1982 300SD. Last weekend it got relatively cold here in St. Lou. I had the car plugged in over night last Friday and drove the car to my cousins house about an hour and a half away. It was 5°F Saturday morning. Car started up without incident. I let the car sit out all day on Saturday. The high that day got to about 20°F. Tried to start it to go home about seven pm that evening and the engine turned over but would not fire. We tried jumping the battery to no avail. As much as I hated to do it, we used ether to get it running. At least I had assitance with the ether so I was able to crank while the help sprayed the ether. I was able to make it home with out incident.

I tried to get the car started on Sunday but no go. Luckily I have the Duramax to use as a back up. The past couple of days I was doing some trouble shooting and here is what I found:

When I engaged the ignition to glow the plugs, I could hear the relay coming in and it went out after approximately 30 to 40 seconds. The glow plug indicator light was not illuminating. Tonight I checked the resistance in the glow plugs and found the reading to be in the megohm range. This is not good. I just replaced the glow plugs earlier this past spring. I replaced them with new Bosch plugs. All five glow plugs were reading in the megohm range. I could not get the car to fire. Luckily I am somwhat of a pack rat so I saved the old glow plugs that I took out this past spring. I checked their resistance prior to installing them and they checked out at 1 ohm or less. I also changed out the relay box. I have a spare that I got from the junk yard. I thougth maybe this was the cause of the new glow plugs to go south. I also checked the 80amp fuse bar in both relay boxes for continuity and visually inspected for hair line cracks. They both checked out ok.

I also checked the voltage on the glow plugs while in the glow mode. All five were reading 13.7 volts. This makes sense I believe, because the glow plugs were not consuming any current because they were effectively open.

After installing the old glow plugs the car fired right up, as it is about 55°F here this afternoon.

Here is my delema. Why did the new glow plugs basically develop infinite resistance? And why did all five of them do this at the same time? Has anyone else experienced this? I think I have provided the proper sequence of events and detail. Could the relay have stuck and kept the new glow plugs energized until they burned out?

I am open to questions and comments. Should I see if there is any warranty on the new glow plugs?