Regardless of which method is used for removing and servicing glowplugs, I'd like to figure out if the results of my tests/measurements point to a healthy glow system or not.

Money is tight, so I'd rather not replace all the glowplugs if I didn't need to. That money could be spent on a new battery OR perhaps on new injector nozzles if dirty injectors are my problem (too much soot in the chambers?)...

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84 300SD - bought in April '06 with 237,000 mi