First check the fuse link at the glow plug relay, then unplug harness and check individual plugs from there. Fuse sometimes looks good but doesn't make connection, so check with test light or volt meter.
Jeff

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1971 R600 Mack toterhome (SuperDawg)
99 NU-WA Snowbird 34+2 SE 102 5er
If it's not diesel, it's not in my stable!
53 F100 617.951/auto
95 Dodge 3500 Cummins/5 speed service truck