Diesel Giant says that the resistance should be 1 ohm or less. I guess I'm having trouble interpreting exactly what it means to have them all test 1.7-1.9 when 1 or less seems to be preferred, at least according to DG.

As I remember testing mine 3 of them were under 1ohm and 2 above so I change out the 2 and have had no more problems.

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1983 300SD
200000miles

Above 1.0 they are junk..

You need a glow plug reamer to clean the hole.



Glow plugs link thread All diesel models
http://www.peachparts.com/shopforum/diesel-discussion/137732-glow-plugs-link-thread-post1019018.html

Where does one purchase a good, reasonably priced glow plug reamer? I see one on eBay for $39. Surely there are cheaper ones out there that still do the good job...

..and I never reamed when I put my new set in this summer.. The old ones came out easily (Beru), they were all good by the way, but what the heck, a couple of the new ones (Bosch) went in "stiff" as they were inserted. At first I wondered if they were correct part, but triple checked and yes. Am I doomed next time I try to get them out?

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Cheers!
Scott McPhee

1987 300D

The reason you use a glow plug reamer is that there is carbon buildup around the tip.
This causes a carbon (insulation) sock to form over the electrode.
The reamer breaks up the shell to powder that will pass through the pre-chamber and out the exhaust pipe.

Here is a thread that should answer the rest of your questions.

glow plug reamer - pic
http://www.peachparts.com/shopforum/diesel-discussion/76490-glow-plug-reamer-pic-post1756147.html