Thanks Klaus, I had not seen this, and I think I've read about 100 threads on the interwebs. It is the second one in which someone is discussing the ECU as the source of the problem. I have been unable to re-find the other post, in which a poster said he replaced the ECU and the problem was solved. I wanted to dig that one up because it had a lot of his tracing steps in it. Pretty sure it was on a UK site.

I did pull the ECU yesterday and examined things, including pins and base, but it was getting too dark and cold to start tracing. NA ECUs are so cheap, I'm tempted to get another and try it, but of course there's no guarantee it won't have the same problem, so need to make sure all the lines are good first. It's so bizarre that so many things failed at once. Solenoid valve was bad, check valve failed, and the pump stopped running, all within a few weeks.