I recently replaced head gaskets on a customers forklift. Once it was back together and time to fire it up no spark. It's a2005 with the 4.3 vortec on propane. As soon as I plug in the ignition control module I lose my 5 volt reference. If however I take the icm off its mount my vref is no longer grounded. I have so far chased every wire in case of a pinch, replaced cam sensor and icm with known good ones and pulled out a lot of hair! There seems to be power going everywhere it should bearing in mind I don't have a diagram for this rig.

The serial number is L005V08098D. Any input would be supremely awesome! Cheers