I went to full synthetic diesel oil on the 84 & 85SD. Starting is not a problem with either car when the battery is charged and glow plugs are working. Dino oil causes problems.

When near 0, I glow twice, turn the key to crank and keep it there. I tap the fuel pedal if it doesn't light almost immediately but crank once only. I'll keep the engine cranking until it starts or the battery dies. So far, this always works. There were times perhaps only with dino oil that the 2nd crank never worked when it was in the low teens or lower. I've read where others say you only have 1 crank.

Remember to check alternator voltage with the glow circuit disconnected when it's cold outside. I've had the parts store test rig condemn the alternator when the only issue was the GP circuit was energized.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.