Does this use a GM module/distributor? I would assume yes since they seem to be pretty common for any sort of EFI conversion, and if so, check the ignition fuse(s), power to the ignition components, etc. The module handles spark under 400RPM (cranking) in the standard GM EFI setups with distributor, if the Powerjection uses the same components, it's probably the same way. Which may help you rule out things like the ECU, etc.
You can google "gm hei testing" or something along those lines if you have the GM ignition setup,pretty easy to test everything. Coil, module, and pickup coil are the big three in terms of parts that fail, but need to make sure power is getting to where it needs to go first.
I know nothing about powerjection, "no spark" should be a pretty easy diagnostic measure to have in whatever documentation they provide if it differs from the GM process. If it's a standard "no spark" condition for a GM setup, the 1987-1991 R/V manuals in the link in my sig will give you the diagnostic charts for no spark.