The light in my SD was taking a second or two to light up after I turned the key to the pre-glow position. I checked my plugs and had one out, now that I have replaced the plug it lights up immediately.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine