Unless I misread, you weren't getting a code from the misfiring injector originally?? Is that a change?
I'm not 100% sure about the code logging thing Andy. The problem is that once it's warmed up, all codes flag, so I'm thinking I could have missed it last time, or mistakenly read a cold logged code as a warm one. I wanted to be sure from last time, which was the reason I did it again from cold this weekend.
I can't think of a better idea than checking pulses to all injectors, or at least the misfiring one and one other and comparing signals when cold.
When the weather is better, I'll get the scope on it, to see if I can get an injector pulse when cold.
I think you have checked compression already. I did wonder about glow plugs, could swap a couple around I suppose as not sure how this engine would react to a duff plug.
Unfortunately this engine uses M8 glow plugs, so I can't fit a compression tester to the plug hole. Also the inlet manifold actually covers the glow plugs, so the manifold needs removing to access them.
I know what an engine with low compression in one cylinder sounds like when cranking, and this engine sounds to have even compression on all cylinders.
I don't know how it would react to a duff plug, but it started with 4 duff plugs and a dead cylinder when I drove it home, so I assumed it should start without plugs, from what I've read, many owners don't know they have a duff plug, until they test them.
I would have thought the PTM would flag a failed plug, but it didn't show it had 4 dead plugs when I read the codes the day I got it home.
Maybe it is so clever it would not fire the injector on that cylinder??
I'm not sure it's that clever.