On my 617 I had all 5 plugs test OK with a meter. But it still started really hard. Put in a new set and problem solved started right up, hmmm. Took the old ones, I think three of them when hooked to a battery only got a little warm. The others turned red like they should.


So from what I have seen even if they test OK they may not be. These looked like original plugs. So in the future when I get a new diesel if the plugs look old I'll just change them and not have to mess with it.

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2006 CL500
1969 280SE
2023 Ram 1500
2026 Genesis GV70
2007 Tiara 3200