Leathermang: Thanks for the advice. No heated manifold here.

Captainmonk and kingdoc: A good question. Mostly it's because the budget is a little tight. Partially, it's because when the car runs and I drive it regularly (1 or 2 times a week), the glow plugs light without a problem. Car hasn't moved for seven weeks at this point.

I've wanted to troubleshoot the problem further to make sure my problem is in the relay itself instead of the wiring connected to the relay, or even in the temperature sensor in the engine block; but I've spent most of my time just trying to get smoke to come out of the back of the engine, which is just not happening.

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'Betsy the Getaway Car' : 1978 MB 240D, 582k
'The Mistress of the Sea' : 2001 Giant Boulder, 10.30k