I would put 5 new BOSCH glowplugs in, regardless. I just did this on mine. Its not a big job, I think it took me about 2 hours, with pulling the intake. Do yourself a favor and get a new intake manifold gasket (mine was leaking anyways), and new fuel line clips (they get brittle and break).

Chances are the glow plug light will come back to life, or you have a fuse/relay problem.

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93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K