I'll bet a simple piezo alarm speaker fom Radio Shack would read the pulse and give a chirp, that would be a simplistic but inexpensive test tool for the sensor. Freeze spray on the sensor and the ignitor would also be a quick diagnostic tool to identify the culprit. And, there's always the mildly insulting "did you check all of the ground wires?"

A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)