Soldered the wires directly
to the injector leads and potted them in epoxy. Replaced the wires
between the EC2 and both sets of injectors with shielded wire, with
the shield grounded at the EC2 end only. That's about it.

Hi Buly,

OK, gotcha.  Not too many changes.  I know it's been mentioned to try the old wires, and I also know what a pain that would be to do.  Have you actually tried that?  If not, do you have a spare injector that you could wire up temporarily?

Basically, I'm suggesting that you disconnect one injector, then temporarily connect a spare injector in it's place.  You'd run 12V to one side, then connect a jumper wire from the other side, to the EC-2 connector that goes to the injector you unplugged.  Put the EC-2 in simulate for the injectors, and see if the jumpered injector works while the others don't.

I admit that I've been skimming through all the posts, so if you've already done this, just disregard this message :-)

Being a retired guy with nothing better to do, I'd think Ed would run down there to give you a hand.  Nah, I'm sure he couldn't fix it (snicker, snicker)  :-)

Rusty (trouble is my middle name)