Thanks for all the good advice. I called Terry at CH and he asked if I'd gone through the trouble shooting routine. Whoops, had not done that yet. The ignition will fire when I turn it on, but not when I ground the white wire and then take it off ground. I was sure that since I'd found the broken blue wire on the hall sensor, that was the problem, but it now looks like it may be the ignition, or maybe both. So, I'm sending it off to CH today.
Keith: Terry says they have the sensor but not the mounting plate. This is my second sensor, and the plate CH provided last time is like a thick PC board cut to shape. I'm not sure if I can find (or if I even have) the old plate that came with the engine. Any chance you have a sensor mounting plate for the old BME44 in stock? If not, I'll re-use the PC board type one.
Thanks again
Sam