I would continue to suspect a bad fuel line. Maybe the ball end of the line wasn't seated properly in the injector cup.

You should replace the injector seal, the nickel size ring that goes between the firing tip of the injector and the prechamber. Drop a magnet or a pick into the injector hole to see if you can dislodge a camouflaged seal. If not, give the engine a quick crank with the stop lever down to see if the old seal blows out.

Kinda hard to describe how to check visually if there's a seal in place. The seal has a smaller hole than the prechamber but the difference is like 5mm for the seal and 7mm for the prechamber.

Sixto
93 300SD