The kit I found has a 10mm, 12mm, 14mm and 18mm adapter. IIRC, the glow plug thread are 10mm or 12mm, should be the same pitch as a spark plug. That will make it where I can test an OM617 easily, and a OM602 with some effort. If I ever do need to test a OM606, I'll just buy that Harbor Freight kit. I guess on an OM606 it's going to be difficult to do any way you look at it, from broken GPs to getting to the injectors.

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Current: 1975 450SEL, 83 300D, 88 Yugo GVX, 90 300D OM603 swap, 91 F150 4.6 4v swap, 93 190E Sportline LE 3.0L M104 swap, 93 190E Sportline LE Megasquirt, 03 Sprinter, 06 E500 4Matic wagon.