Don't forget to check the fuse also in the relay box for the glowplugs. I had a similar problem and replaced the glow plug harness, and all glow plugs and in the end it was only the fuse. since im only a tinkerer and only learned what i know about my 81 240d on this forum here and diesel giant. good luck

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94' Blazer - Totaled
03' Neon - Dead now totaled! ps. Easy to flip
81' 240D 144000k - Beast - SOLD and Saved from scrap heap!