Just got an 86 190D, Cylinder 3 doesn't fire when hot. help?

[xweezyx]

Hi everyone. I just got an '86 190D 2.5. Its very nice, very little rust, glides down the highway, but heres the story.

The car has been sitting for at least 6 months. It started right up with a new battery and doesn't smoke. The former owner, who passed away, was an airplane mechanic, and installed a fairly decent WVO system. It stalled on me on the way home, so I decided to take out the system. It was a main tank conversion, so I emptied the tank, and filled it with B50, changed the filter, etc.

Now it starts, runs without stalling, Idles, slow, but pretty smoothly with the exception of an obvious cylinder misfire. I loostened each fuel like one by one, and the one for cylinder 3 had no affect on the idle. The next day after I swapped injector 3 with 2, started it up, all cylinders seemed to be firing. I figured that maybe the B50 cleared it up? went around the block a few times... Cylinder 3 is not firing again. The injection pump appears to be squirting just fine too. I guess next I should get a compression tester and test cylinder 3, but somehow that doesn't seem likely to me. I'm going to run diesel purge soon, but I'm not sure if that would help. its a 150,000 mile car that seems perfectly healthy other than this. any ideas? thank you.