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Warning: that $89 glow plug tester almost cost me a head gasket
I was chasing a cold start miss on a 7.3 and picked up one of those cheap inline glow plug testers off Amazon. It showed all 8 plugs were fine, but the truck still cranked like a dying battery. Turns out the tester was reading voltage through the bus bar, not each plug individually, so a bad plug on cylinder 6 slipped right past. I pulled the harness and tested each plug with a multimeter, found the dead one, and swapped it. Cost me two extra hours and a near misdiagnosis that would have had me pulling the intake for nothing. Has anyone else had a tool that gave them a false sense of security like that? I'm going back to the simple test light from now on.
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lucashenderson24d ago
Been there with a cheap test light that lit up on a circuit that had a broken wire inside the insulation. Showed good voltage but couldn't carry any load, so I chased my tail for an afternoon thinking the relay was fine. Those inline testers are the worst for glow plugs though, they just read the whole bank and hide the one that's actually dead. You did the right thing pulling the harness and checking each plug one by one. Honestly a plain test light and a meter will beat half the junk tools on Amazon every time.
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