This is part of my C280 revival thread posted in the Tech section speaking about a miss fire I'm chasing.

. . . Got exhaust back up, ran engine and it has a ragged miss that turned to a dead miss. Pulled injector wires found # 2 cyl not firing. Swapped the inj feed with # 1 and still had 2 not firing. Hooked a test light between bat + and inj plug, the light would flicker at idle then went out after about 15 sec. ( more about this later ) Triggered the injector with 12V, the pintle clicks but no fuel is injected. If I scratch the jumper to cycle the inj the cyl tries to fire. This car sat for 3 years so old fuel damage the issue. Next up is swapping all inj from the spare engine I have.

As for the 15 sec to dead miss. The ME SFI 2.1 engine computer shuts off the injector to a cylinder that is miss firing so , if the miss is caused by ignition , raw fuel does not over heat the cat. Clearing this requires cycling the ignition. Miss detection is part of the OBD 2 standard so all it takes is a bit of software to accomplish this.