Are all the glow plug wires and connections sound? Dougmcp's suggested method of testing the GP's will tell you. That's the method suggested by the factory service manual.

Do the glow plugs have power? You should have 12 volts between the relay output pug connections and ground.

If not, check for continuity across the strip fuse on the relay.

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1985 300SD, 203,000 miles, dark blue

Lil Sarah says: "Poor old Grandma Blue Car...She's sad."