I have identified the wire for you that goes between the glow relay and the terminal block. It should not go anywhere else per the FSM. To check if that's true, you have to disconnect both ends of that wire and buzz it out to battery + cable, or the hot side of all fuses. If you get a reading, someone has tampered with it and tapped into that wire. It doesn't hurt to add another wire in parallel, but if it were my car, I'd want to know if that wire has been tampered with.

Try a long nose vise grip or dikes on the screw. That's a #3 Phillips btw. Using a #2 bit is probably why it's rounded.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Put a flat blade screwdriver under the screw head slightly prying up as you try to unscrew it.
Sure sounds like someone has been in there before for some reason.

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1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

That's my sentiments also. I'll try getting some vice grips on there, I don't mind replacing the terminal block, if I can even break the screw off or drill it out I'll connect it all together temporarily and buy a new one.

I'll have a fight with it Here in a minute. I'd just like to know what has been done to the car. Id rather knowingly be driving a lemon (my 124 was given to me because of all the issues it had/has) and know its story than have a surprise a few hours from home.

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1982 300D (w123, "Grey Car")
1982 300D (w123, "Blue Car")
2001 Ford F150 "Clifford" (The Big Red Truck)
1997 Dodge Ram 2500 12V Cummins
1996 Dodge Ram 2500 12V Cummins
Previous Vehicles:
1995 E300D, 1980 300SD, 1992 Buick Century, 2005 Saturn Ion

Sorry guys, I haven't done anything more to the car yet.

My wife got into some poison ivy real bad, I'm not allergic so I've been helping her clean it and it's not getting much better, only been a couple days but we've got to go to the doc today and see if they can give her a shot or something for it, its all over her arms and its spreading...

Now that I'm done grossing everyone out, I'll be back on the car after she's better, she won't be driving it like this, she can barely bend her arms.

I'll keep you all posted on what I find out about my wire issue

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1982 300D (w123, "Grey Car")
1982 300D (w123, "Blue Car")
2001 Ford F150 "Clifford" (The Big Red Truck)
1997 Dodge Ram 2500 12V Cummins
1996 Dodge Ram 2500 12V Cummins
Previous Vehicles:
1995 E300D, 1980 300SD, 1992 Buick Century, 2005 Saturn Ion

I wish her well.Maint. on glow plugs,wires will be broken sometimes,on the plug,glow plug relay is replacable,I went with the new model,that stay on for a while.Water temp wire can break also,the glow plug relay uses it.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

If the glow plug wire has not been tampered with, i.e. cut in the middle and tapped into by whatever means, then the problem may be with the crimps on both ends. If you are ambitious, you can peel back the insulation, clean the crimp with a wire brush, de-grease it, soak in a solvent for copper oxide then solder it well with a lot of flux. That will restore those connections.

Regarding poison ivy. I got a bad case of it when I started rock climbing years ago. The approaches to the climbs are often laced with poison ivy. I learned real quick how to identify it summer or winter and have never gotten it again. I can spot that stuff a mile away.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I am finally ready to update this! I found the problem today. I did as recommended and used vice grips to loosen the stripped screw, worked a charm!

Cleaned everything up, still 9.7ish volts at the relay. Checked at the terminal block, coukda sworn I checked voltage there too, and it was also low. The wire that feeds the terminal block from the starter was the problem. Now I've got a much healthier 11.9 key off and 10.7 with the relay switched on. Car starts nice and easy.

My next thing to tackle is I believe I have a slight air leak in the fuel system, I've replaced the return lines on the injectors, as well as the cigar hose and the rubber line before the primary filter.

I'm hoping its not the steel lines or something, but here's what it does: when you first start it in the morning you have to just touch the throttle with your foot. Without that slight pressure it won't start. After it starts it runs smooth as long as you keep just a tiny bit of pressure on the pedal. If you let off the idle drops drastically and stalls.

I replaced the primer pump with one off my spare engine, as the old one was leaking diesel out of it. That made it so you had to hold your foot on the pedal for less time, but its still about a minute before it'll idle smoothly.

Is it possible the valves need adjusting? Could that cause this?

Thanks a lot for the help with the glow plugs guys, I'll have some questions soon about my w124 as I've just ordered a pile of stuff from pelican for it. Engine mounts and stuff.

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1982 300D (w123, "Grey Car")
1982 300D (w123, "Blue Car")
2001 Ford F150 "Clifford" (The Big Red Truck)
1997 Dodge Ram 2500 12V Cummins
1996 Dodge Ram 2500 12V Cummins
Previous Vehicles:
1995 E300D, 1980 300SD, 1992 Buick Century, 2005 Saturn Ion