Got the engine running on woodchips last night! I've been studying and researching this stuff for years, and I've seen other people do it, but still, getting an engine running on woodgas in my own backyard is incredibly satisfying. 

I tightened up all my connections, and they all seemed to hold up much better this time. I also ended up with considerably more liquid than I expected in the tar trap- about 1/4 of a liter just from maybe a gallon or so of woodchips.

When I cleared out the keg to put the new woodchips in, I found that the old batch had become a very nice, very completely-pyrolyized biochar!

Success! Next steps are to get my 8HP propane engine running on woodgas, and figure out some sort of low-pressure gas storage system to even out differences between gas output from the reactor, and gas consumption from the engine.