Wow, I'm surprised that PEH accepted your glow plug test and went on to harder stuff. It has been reported here a number of times that glow plugs can test good and still not work. The ultimate test is to remove them from the engine, put 12 volts to them and see if they glow red hot within a few seconds. If you want to do PEH's injector line test, it will tell you which plugs to pull.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References