One of my two 83 300D's wouldn't start this morning. It was .6 degrees F and I had the car on the heater for about an hour and a half before trying to start it. The ignition switch in the car was very stiff, the glow plug indicator would go on sometimes, flicker some and on a few occasions not go on at all. Question one, could the ignition switch be going south or is it more likely a GP relay/GP issue? Question 2, where on the 123 is the actual relay and can it be cleaned/tweaked? Question 3, the car has the pin type GP's and I'll most likely be replacing them. Is the reaming tool absolutely necessary to clean out the GP hole? The car is regularly driven at 80~85 MPH and is in frequent use if that does anything to help keep it clean inside. Is the GP relay super expensive? Is there some kind of GP kit that leaves the GP's on for like three minutes or so to help with warm-up?
The other diesel, actually a 300CD, started after being plugged in for 30 mins. It started unhappily but it did run and I was able to use it today.
Too damn cold to fix anything, but maybe we'll get a quick break soon.
Thanks for any and all advice.

It is most likely a GP issue.

The relay is on the forward side of the left fenderwell. It is a rectangular box with a removable cover. It has a plug with five sockets that plugs into it for the glow plugs. It cannot be cleaned or tweaked AFAIK.

Personally, I've never used the reamer nor have I needed it. You won't know until you try and remove the plug whether the carbon buildup is excessive.

Well, super expensive is relative. I believe a new one is about $140. or so, but, I have not checked lately.

Yes, there is a kit. It does require the replacement of the relay. Phil can help you obtain this kit. The kit will only help smooth out the idle after the engine is running. I'm not convinced of the necessity of the kit for the 617.
In any case, the kit will not assist in a cold start.

They are cheaper than a relay.

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