Used glow plugs must be tested before installing.
I junk any that read higher than 0.7 OHM and/or fail to (bench test) glow correctly.

Here are all the pictures and technical material you need for testing.

http://www.peachparts.com/shopforum/2360231-post8.html

http://www.peachparts.com/shopforum/diesel-discussion/134359-never-touch-hot-diesel-glow-plugs.html#post986836

http://www.peachparts.com/shopforum/2611938-post13.html

How do Glow Plugs work? | Ask Pete

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

http://www.peachparts.com/shopforum/diesel-discussion/104547-glow-plug-testing.html

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__________________
ASE Master Mechanic

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
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1985 300SD
1983 300D

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